Tracking mount for long lens

Looking for a tracking mount that will support my DSLR and 400mm w/ 1.4x so I can start doing some deep sky photos. I read about the Ioptron Skytracker but don't know if it will support it. Will it? Any other recommendations? Or would it be more cost effective to attach the camera to a tracking telescope?

shane_c wrote in post #18251159
Looking for a tracking mount that will support my DSLR and 400mm w/ 1.4x so I can start doing some deep sky photos. I read about the Ioptron Skytracker but don't know if it will support it. Will it? Any other recommendations? Or would it be more cost effective to attach the camera to a tracking telescope?

I suspect that most tracking mounts will not track accurately enough (i.e. give you nice, round stars) for more than a few seconds at 560mm focal length.

At a focal length of 560mm, you will not only need “tracking”, but also “auto guiding” to ensure that you do not get star trailing.

Tracking: the motor simply drives the mount at 1 revolution in approx. 24 hours, to compensate for the earth’s daily rotation. There is no feedback to the mount, it simply tracks at a predetermined rate.

Auto guiding: a separate, small guide scope records an image of a star field on a guide camera every 5 to 10 seconds. When a selected star begins to drift off a nominated pixel, the guide camera activates the motor by a small amount to return the guide star to the pixel location. This feedback every 5-10 secs is what will give you nice round stars for exposures of longer than say 20 to 30 secs at 560mm.

Cheers

Dennis

shane_c wrote in post #18251159
Looking for a tracking mount that will support my DSLR and 400mm w/ 1.4x so I can start doing some deep sky photos. I read about the Ioptron Skytracker but don't know if it will support it. Will it? Any other recommendations? Or would it be more cost effective to attach the camera to a tracking telescope?

What's your budget and how much weight are you able to tolerate moving?

The new SkyTracker Pro could do it. But it will also be a limitation if you really get into it and want to go deeper and longer with the genre.

Very best,

I don't think an iOptron tracker can handle the weight. The Sky Watcher "Star Adventurer" might handle the weight (might) if you have the counterweight bar (it's an accessory) to help balance the load. The Losmandy "Star Lapse" can probably handle the weight (it's really the head from a Losmandy GM-8 telescope mount adapted to hold a camera and fit on a normal photo tripod). But my bigger concern is if the tripod can handle the weight without flexure issues.

You're trying to handle a 560mm focal length and as the focal length increases, the precision of the polar alignment becomes more critical.

My Andromeda galaxy (M31) photo was shot using an APS-C camera (Canon 60Da) attached to a TeleVue NP101is telescope (540mm focal length) and those were all 8 minute exposures. But... it was mounted on a Losmandy G11 mount (_very_ sturdy mount which is well-liked by astrophotographers for it's performance.)

The iOptron SkyTracker Pro can handle 6.6lbs. The 400 F5.6L + 60D is 4.23lbs. It can handle the weight. All these trackers are going to struggle with the focal lengths of 400mm on an APS-C without ideal conditions, including the Star Adventurer.

Just depends how compact, how many built-in features you want, etc. If I were backpacking, the new SkyTracker Pro is pretty attractive.

400mm on APS-C is still pretty long, plenty long for the larger DSO's. I wouldn't even use the 1.4x TC.

Very best,

Thanks for all the replies! It will give me lots to think about.

Just to be clear... while I have taken many shots using a tracking head, I have never taken one at a very high focal length (typically the 135mm is the longest but considering I've gone 8 minutes with no elongation due to tracking issues, I have no doubt I could go higher... 200mm... maybe even 300mm.

High focal lengths will be challenging and you may have issues regardless of which tracking head you choose because you are (more or less) in the category where you should be thinking about a telescope mount rather than a photo tripod with a tracking head.

I've seen cameras mounted to telescopes using and adapter and I've also seen some piggybacked on the telescope but using its' tracking mount. Is one way better than the other?

Also, I was reading online that not all tracking telescopes can be used for photography because the type of mount would limit you to 20-30 second exposures. Is that true? Could it still be done, just that you would need more shorter exposures vs fewer long ones? What should someone look for in a telescope they want to use for photography?

Sorry about all the newbie questions.

shane_c wrote in post #18260620
I've seen cameras mounted to telescopes using and adapter and I've also seen some piggybacked on the telescope but using its' tracking mount. Is one way better than the other?

Also, I was reading online that not all tracking telescopes can be used for photography because the type of mount would limit you to 20-30 second exposures. Is that true? Could it still be done, just that you would need more shorter exposures vs fewer long ones? What should someone look for in a telescope they want to use for photography?

Sorry about all the newbie questions.

You've received some great advice already but for anyone to provide realistic information it would be most helpful to know your budget. But for now here's something to think about. The Losmandy G-11 was my choice but the mount and tripod will run you over $3,000 US, a used one would obviously be less. With careful alignment and gear balance I can easily get 4 minute exposures with mine at 400-500mm in focal length. That's with no auto guiding, just the tracking mount doing its thing. You're not talking about a heavy gear load so a Losmany G-8 or something comparable would be fine and would offer a little room to grow. In making your choice watch the mount weight restrictions, cut that number in half for photography at moderate to high focal lengths.

While shorter exposures will help preserve exposures from signs of movement they're also data challenged. Each exposure can only add to a combined "stack" of exposures the data present in that frame. The light gathered in a 20-30 second exposure is limited, so stacking 50 of them will result in limited detail. Stacking cannot create details that each individual frame does not contain. The darkness of your skies will play a role in your exposure times as well, dark skies are extremely beneficial to the process. Light pollution filters help but they're no substitute for dark skies.

Hope this helps in some way.

Nighthound wrote in post #18260645
You've received some great advice already but for anyone to provide realistic information it would be most helpful to know your budget.

I was thinking $1000 range.

So I'm guessing something like the Celestron Nexstar 6SE wouldn't be very good then.
http://atlanticphotosu​pply.com …[product_guids]​[0]=612192

shane_c wrote in post #18260710
I was thinking $1000 range.

So I'm guessing something like the Celestron Nexstar 6SE wouldn't be very good then.
http://atlanticphotosu​pply.com …[product_guids]​[0]=612192

If your wanting to stay under $1000.00 then you might check into the Celestron Advanced VX Mount . Holds up to 30-lbs of equipment and has three star alignment . Rather simple to operate . Can be used with an Auto-Guider bought seperately . It can handle just about anything you have as far as camera equipment and if you decide you wanted to buy a optical tube (telescope) you can always buy one and use this mount . A good 8" SCT or a 4"-6" refractor tube would work nicely on this mount .

http://www.celestron.c​om …tripods/advance​d-vx-mount

A different approach. I recommend the Astrotrac TT320X-AG. This equatorial mount will handle 15 Kg, 33 pounds, although convention dictates if it is rated for 33 pounds, stay under half that or 16 pounds. It will handle your 400 with ease. For most deep sky applications, with a crop camera, you will not need a telextender. The total for this mount is around $750.00.

It is also quite portable and easy to set up in the dark. It comes complete with polar alignment scope using either two or three star alignment error.

Google this mount and read about it. Many are in use in the field.

shane_c wrote in post #18260620
I've seen cameras mounted to telescopes using and adapter and I've also seen some piggybacked on the telescope but using its' tracking mount. Is one way better than the other?

Also, I was reading online that not all tracking telescopes can be used for photography because the type of mount would limit you to 20-30 second exposures. Is that true? Could it still be done, just that you would need more shorter exposures vs fewer long ones? What should someone look for in a telescope they want to use for photography?

Sorry about all the newbie questions.

BEEFY SOLID GEAR... that's what you want if you want to do astrophotography with a telescope. The mount is actually more important than the scope (not that the scope isn't important, but the mount is more important.) Do not short-change the mount or you'll start to run into all sorts of issues that give you buyer's remorse (I speak from experience on this topic.) If I had it to do over again... no matter how poor I was, under no circumstances would I consider any mount that costs less than $1500... and that's the bare minimum. If I could spend $2000... or 3000... or 4000... I would.

Then there's the scope.

There are three major categories of telescope design types... "refractors" (use all lenses to focus the light), "reflectors" (use all mirrors to focus the light), and "catadioptric" (use a combination of lens and mirrors -- sometimes just called "compound" scopes for that reason.)

In refractors, there are two sub-categories... "achromatic" refractors and "apochromatic" refractors.

When light passes through any glass "lens" the curvature of the lens surface acts like a prism and creates an undesirable side-effect called dispersion in which different wavelengths of light bend different amounts and technically focus at different distances. The simple method to correct for this is to use a 2nd element in a configuration called an "achromatic doublet". The 2nd lens element has a concave curve instead of a convex curve. It doesn't completely fix the dispersion problem and you will find that objects near the edge of the field of view (stars in particular) show some color fringing as the lightwaves are all focusing in slightly different spots depending on the color/wavelength. Achromatic refractors are typically very low cost.

The "apochromatic" scopes do a significantly better job correcting. There are lots of variations of the design. Some use extra-low dispersion glass (aka "ED" glass). Some use three elements. Some use both. You can tell the difference in scopes by the price tag.... whereas an achromatic refractor might cost a couple of hundred dollars... an apochromatic refractor is typically at least $1000 (at the low end) and the price goes up from there (they can easily cost several thousands dollars.)

For visual astronomy, the achromatic scopes are good enough because you'll almost certainly just center the object that you plan to observe. But for imaging with a refractor, you _really_ want an apochromatic refractor. You (and everyone else) will immediately notice the difference.

Reflectors don't have the dispersion problem because the light never passes "through" glass. The mirrors are glass but the reflective coating is on the front surface -- not the back surface as it is in most common mirrors. That's "good" because you don't have to deal with dispersion issues. But it's "bad" because that surface is extremely easy to scratch (so handle with care... never use ordinary cleaning products on the mirror.)

One major issue with reflectors is that most reflectors are of the Newtonian variety and the eyepiece goes on the side. The challenge when thinking about these for astrophotography is that if you're using a DSLR, there's about 50mm (roughly 2") of extra distance from the front of the camera body (the lens mounting flange) back to the image sensor. This is to allow room for the reflex mirror. The scope, however, is designed to bring an image to focus at a set distance... a 500mm focal length scope means that 500mm after the light bounces off the primary mirror, the image will come to focus. The internal space of everything is designed to deliver a focused image at the eyepiece. When you attach a camera, the focus plane is really about 2" farther back. To compensate, you have to rack in the focus by 2" and most focusing mechanisms don't have enough travel... they hit the limit as the image was only starting to come to focus and then you run out of travel.

There are reflectors designed specifically for astrophotography and all they really need to do is move the primary mirror forward to compensate (and possibly fractionally enlarge the secondary mirror). The scope can still be used for visual use if you add a 2" eyepiece extension on the front.

Both refractors and reflectors tend to be somewhat short focal length scopes... 500mm... 600mm... maybe even 1200mm... but they're usually less than 1500mm (otherwise it would need to be very large).

Compound scopes (sometimes astronomers call these "CATs" - short for Catadioptric scope -- such as Schmidt Cassegrain Refractors (aka "SCT")) generally have very high focal lengths... whereas an 8" Newtonian reflector might have a 1200mm focal length, an 8" SCT will probably have a 2000mm focal length. I have a 14" SCT and it has a 3556mm focal length. These CATs are good at imaging small things. They're great for imaging planets and small deep-sky objects such as galaxies or some of the smaller nebulae. For large nebulae the object usually wont fit in the field of view.

Just remember... the higher the focal length, the more intolerant the scope is regarding tracking errors or vibrations... it takes hardly any movement at all to smear the image at these high focal lengths. My suggestion... start with a shorter focal length scope first.


On the issue of mounts...

Even among telescope mounts there's the question of how well it handles the weight. Some low-end go-to mounts aren't that solid... wind would be enough to shake the scope & camera. There's also an issue of "balance" when you piggy back. The mount can struggle to move an unbalanced load because on low-end mounts the motors, gears, and clutches aren't very strong.

In "go to" category of mounts (mounts that can point to objects and track them automatically) there are mounts in an "alt/az" vs. "ra/dec" orientation and this is a really important difference for astrophotography.

Alt/Az mounts

"Alt/Az" or "Altitude & Azimuth" are the simplest to understand because they look like simple turrets... you can rotate in 360º and it tips up or down. Sounds simple enough. But there is a big catch.

The "catch" is that neither of two axes of movement are in any way related to how the Earth spins UNLESS you happen to be located on either the North pole or South pole (we can probably safely assume you wont be.) If you think about the rectangular "frame" being level to the horizon at sunrise in the northern hemisphere, the Sun does rise "straight" up... it move at a diagonal moving up and to the right. And yet at sunset, it's moving at a different diagonal... this time down and to the right. The Sun's axis isn't really change... only our perspective angle of the Sun is changing and that's due to the rotation of the earth. This means the axis of the sun must be slowly rotating through the day. I picked on the Sun, but it applies to every object in the night time sky. If you view the sky through the camera you wouldn't quite notice it because it happens very slowly... but a long enough exposure WILL notice it -- the sky appears to "twist" as the camera tracks. This "twist" is called field rotation.

Major professional observatories do use alt/az mounted telescope because it's easier to support the massive weight of these enormous scopes. So to counter act the problem, the camera is actually mounted on a device that can rotate the camera itself as the telescope tracks. This is called a "field de-rotator". The speed at which it has to rotate depends on where it is pointing in the sky. Objects near the horizon seem to rotate less than objects near the zenith. A computer has to calculate the proper rate of rotation (and it's constantly changing.) Meade used to sell such a device for their LX200 series scopes (it used to cost about $600) but it's a discontinued product.

Equatorial mounts:

Equatorial mounts are tilted over at an angle. The lower axis (called the "Right Ascension" axis) it tilted over at an angle that matches your latitude on Earth. So if you live at +40º north of the equator, then that means the celestial pole is 40º above the horizon. So the right ascension axis is tilted so that if you could draw the imaginary axis upon which everything rotates, that axis would go through the north celestial pole in the sky (a point very close to Polaris).

In doing this, the axis of the Earth's rotation and the axis of the mounts rotation are now EXACTLY parallel to each other. As the Earth spins from west to east, the mount spins from east to west (opposite directions) and they also rotate at exactly the same rate. This perfectly cancels out the spin of the Earth AND also does it in a way that you have no field rotation. You can image as long as you want (assuming a precise alignment) and get no blur caused by the movement or twist of the sky.

While it's a bit difficult to wrap your head around what an equatorial mount is doing... it's actually easier to use once you realize what it's actually doing (if your brain is still stuck in the alt/az world then it will frustrate you). The right ascension axis is actually move the scope or camera in a PERFECT east-west direction. In other words if think of Earth's lines of latitude and longitude -- except not on the ground... in the sky (we call this the equatorial grid) the axis is moving along those lines of imaginary "latitude" (east-west running lines).

The other axis is called the "declination" axis. It's simply adjusting how far north or south the mount is pointing. A declination of +90 means you're pointing at the sky directly above the north pole. A declination of -90 means you're pointing at a section of sky directly over the south pole. A declination of 0º means you're pointing at the sky somewhere directly above the Earth's equator.

In other words... moving in RA is simply an east/west adjustment and moving in Dec is simply a north/south adjustment.

While it's not the way our brains normally like to think of a two-axis mount (we like things to be level with respect to the ground we're standing on and the equatorial mount is basically "level" to the axis of the Earth itself... never mind the particular piece of Earth you happen to be standing on) this arrangement works out EXTREMELY well for astrophotography.

Camera "tracking heads" like those made by iOptron, Sky Watcher, Losmandy, and Astrotrac are all designed to be tilted on that angle (just like an equatorial mount) but they only have a single motorized axis -- the RA axis. Once your tracker is set up correctly with a proper polar alignment (so it's rotation properly cancels out the rotation of the earth) you can attach a ballhead to the tracker and this lets you point the camera to any piece of sky you want -- you don't have to point the camera at the north pole.

Here's a single 8-minute long test shot (I stopped down to f/8 with a 135mm lens) to get this. In reality I used f/2 and much shorter exposures to capture the data for this region of sky, but the 8 minute shot let me validate that my stars were not elongating ... which meant I had done a good job aligning the axis of my tracking head to the north celestial pole -- even though THIS region of sky is nearer to declination 0º (above the equator - so I'm not pointed anywhere near the north pole.)

shane_c wrote in post #18260710
I was thinking $1000 range.

So I'm guessing something like the Celestron Nexstar 6SE wouldn't be very good then.
http://atlanticphotosu​pply.com …[product_guids]​[0]=612192

Heya,

Light weight or Sturdy. Pick one.
Inexpensive or Accurate. Pick one.

Nothing wrong with a $1k budget. You just have to put it into perspective of what you can do within that range.

I would argue against getting an AVX new. If you find one used for $500, go for it. But if you're buying new, the HEQ5 or Sirius would be the minimum I would suggest and honestly, I would really just suggest you pinch pennies and get an EQ6 or Atlas or CGEM if you were truly going this route. The mount is the most critical part of the imaging setup. It's the great limiter of everything you will be able to do. Get as much mount as you can first. You can always image with a camera lens on it for a while. But you cannot use big instruments on light weight mounts with lesser worm gears and components. You need quality if you want it to work, accurately, and last. Look for used!

If you want to track the moon, sun, planets, the Nexstar range is a nice visual mount for cheap, and you can do video astrophotography with it. It lets you get a taste. I would consider it more a visual mount though, meant to keep your long focal length on target longer so that you can actually view it instead of fiddling with something manually. They are worth considering. I have a 6 inch SCT and the views are excellent, lots of aperture for such a small scope, and it's very portable, light weight, and easy to use and find things.

If you want to expand into deep space (DSO) and do long exposure photography, then I would go a different route.

If you want to stick to camera gear, the StarAdventurer or iOpton SkyTracker Pro are great options.

If you want to get into telescopes, the Nextar series is a nice toe in the water option with tracking, but it's inexpensive for a reason (you can get the mount for $350~500!). It's not going to hold weight, it's not going to track well, it's not going to be accurate. They're good visual tracking mounts for bigger scopes. They are not really good imaging platforms. They can produce images, yes. But there's a difference between "it works" and "this is what serious imagers use." I like the Nexstar series, it's excellent for visual. You can get a wifi module and control it from your phone or tablet! Very cool mount for the money. But don't consider it a serious imaging platform. So if you want to image with telescopes, it's going to cost you $1500 just for a mount, minmum, and really it's going to cost you $2500~3000 for a full imaging setup with everything needed.

Very best,

Thanks for the replies! I've decided not to get into deep sky photography. But I'll certainly keep lingering around this section and admiring the great photos.