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FORUMS Photography Talk by Genre Astronomy & Celestial Talk
Thread started 09 May 2017 (Tuesday) 12:36
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there is an old thread time for a new Best Scope for a Beginner

 
dashotgun
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The Tar Heel state
May 09, 2017 12:36 |  #1

I am recently retired always wanted to do astro photography what is good for around 1000 I have a 7d and 7d mark 2 several lenses. tia


You don't take a photograph, you make it. ~Ansel Adams
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Celestron
Cream of the Crop
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Joined Jun 2007
Texas USA
May 09, 2017 14:50 |  #2

dashotgun wrote in post #18350111 (external link)
I am recently retired always wanted to do astro photography what is good for around 1000 I have a 7d and 7d mark 2 several lenses. tia

dashotgun for under a $1000.00 that maybe hard to find a complete setup that is really a nice scope . Myself I am partial to Celestron scopes cause their optics are some of the best optics at a more economical consumer price . If you could swing just a little more Celestron has one that would be great for a beginner in a SCT build :

http://www.celestron.c​om ...midt-cassegrain-telescope (external link)

6" is very popular because of the FOV (Field Of View) and aperture size . Also this one comes with a Go-To tracking mount which is a big plus and it has Auto Align in the computer data base making it easy to setup and Polar Align so you can get started easier and faster . All you would need with this is your camera and you would have to buy a T-Ring that takes the place of your camera lens and an adapter that attaches the T-Ring to your scope . That would be about $50.00+ more investment for photography use . The scope will come with everything including one Eye-Piece (EP) to start visual observation . Anything else you would have to purchase or if you wanted more different size EPs' you would have to buy those extra when you want to . Now as I say this one is a SCT (Schmidt-Cassegrain Telescope) which uses mirrors and not glass lens .

Now others will suggest other scopes and maybe a refractor which will be a longer tube and uses glass lens instead of mirrors . But they do produce a much more clear and crisp image than a SCT . Two kinds of refractors , one is a Chromatic Refractor and the other is a Apochromatic (APO) refractor . APOs' are usually very expensive but have fine glass and produce great images . The Chromatic Refractor has glass of minimum requirement but because of the low quality glass used your images and while viewing will have CA (Chromatic Aberration) which is a purple or blue haze around bright objects like stars or planets , this makes imaging very unpopular cause in most cases the CA is hard to remove through PP . The APO scope will either have none whatsoever or will be so hard to detect you wont either see it or will it show up on images . ANd most times the mount that comes with these Chromatic scopes will not have a Go-To mount unless you order it with one and minimum cost of a Celestron Go-To mount is $799.99 :

http://www.celestron.c​om ...tripods/advanced-vx-mount (external link)

Astroimaging can become very expensive hobby so before you actually make a purchase I would suggest you go to a Star Party if you have one near you or find someone that might live close to you that would let you join them for a night of observing or imaging . There are other mounts you can buy and use a camera tripod but for the cost of them you can buy a nice scope for a little more cost and have a scope you can observe with when not imaging with a Go-To mount and have a very nice setup . Others may suggest a lot more expensive mounts and setup but since your trying to stay under $1000.00 you should make real sure you want to invest a lot of money and time before you get into those high cost mounts and scopes . That way if you decide to go another direction you may save yourself a lot of $$$ . Good luck tho , There are lots of brands of scopes and mounts so be picky and don't settle for less than the quality you expect . Just like camera lens , you get what you pay for !

https://www.astronomic​s.com/ (external link)

https://explorescienti​ficusa.com ...ource=Bing&utm_medi​um=CPC (external link)

http://www.telescope.c​om/home.jsp (external link)

http://www.stellarvue.​com/ (external link)

https://www.optcorp.co​m/telescopes.html (external link)




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TCampbell
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Joined Apr 2012
May 11, 2017 10:41 |  #3

The mount stability is very important and this tends to drive up the cost of a decent astrophotography rig. But there are "tiers" of astrophotography and it can be done with many different budgets as long as expectations are in line with the budget. I do want to mention straight away that $1000 isn't much for an imaging setup. I did an academic exercise in trying to come up with a basic imaging setup for merely $2000 a while back and found that I really had to compromise on the quality of the gear and wouldn't be willing to buy that gear myself. I tend to caution about what sort of expectations you should have if you buy any mount for astrophotography where the mount alone costs less than $1500 (and that's just the mount... no scope). A more realistic minimum budget for a mount, scope, etc. is probably nearer to $3000. However, you can certainly capture some fantastic images for less than $1000... I'll describe an option for less than $400.

The rotation of the Earth has to be cancelled out to allow long-exposure images without blurring the stars and everything else in your image. An "equatorial" mount rotates the camera in telescope in the direction opposite of Earth's rotation. So as the Earth is rotating from West to East, the mount is rotating from East to West at the same speed. If the mount is set up so that it's axis of rotation is parallel to Earth's axis of rotation then they cancel each other out and you get a nice image... it's a beautiful thing.

Tracking heads:

One of the most affordable ways to get into this is to simply buy a "tracking" head for a photography tripod. Ideally the photography tripod is quite solid so you're not dealing with vibration and flexure issues while trying to take photos that last several minutes per exposure (and you want many of these exposures... ideally about 2 hours worth... but 4-6 hours would be even better.)

Sky Watcher makes a tracking head called the "Star Adventurer". The head is about $300 (give or take) but there are a couple of accessories that are inexpensive and worthwhile. One is an equatorial base that allows you to more precisely adjust the angle of the head to match your latitude on Earth. There's also a declination mounting plate and counterweight bar (and weight). This allows you to balance for better tracking.

Such a head simply needs a camera and lens - there is no telescope. You would take wide-field imaging... but for astro-imaging, even 200mm focal length is considered very wide-field.

The other big vendor in this space is iOptron and they made a Sky Tracker head as well... but the Sky Watcher head was significantly better. Consequently, iOptron has now redesigned their head and the newer model is called the "Sky Tracker Pro". I know many people who have the Sky Watcher head. I do not yet know anyone who has the "new" iOptron Sky Tracker Pro head.

The option (assuming you already own a solid tripod and some camera lenses) will run just under $400. Also, they're very portable (I take this type of setup with me when I go on vacation).

Here's an example from a bit over a year back when I went to Maui. A friend has access to "Science City" (the area with all the observatories on top of the Haleakala volcano) and I captured this:

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Photo from TCampbell's gallery.

This was shot with a Canon 60Da using a 135mm lens. I'm using a tracking head (in my case it's a Losmandy StarLapse tracker) and a solid Manfrotto tripod (it is a larger photographic tripod... not a budget model). Though that image was captured using shorter exposures, I did test the setup across longer exposures by dialing down to f/11 and testing it for 8 minutes. I was getting great tracking even across an 8 minute exposure.

The point is, it was light and easy enough to travel with. I wouldn't have been able to easily bring a bigger setup.

Telescope Mounts:

Up from there you get into telescope mounts... but this starts to become more challenging. As the focal length increases, the tracking performance becomes critical. This means you usually need to add an "auto-guider". The auto-guider is a 2nd camera and usually a second scope (ideally it would be about 50% of the focal length of your imaging scope... but it could be as low as 1/3rd of the focal length and still be fine.) The guide camera takes frequent exposures of the star field and is tracking on just one star. So while you might be taking a 5 or 10 minute long exposure with your DSLR... the guide camera is taking another image every few seconds. It compares each image with a master image to detect if the guide star appears to be drifting -- even at a sub-pixel level. If it is drifting, it sends a corrective movement command to the telescope mount. This keeps the main imaging camera on target so the you don't see elongated stars or blurring due to poor tracking.

But this also assumes the mount is capable of good tracking and this is tricky. My first mount was a Celstron CG-5 (Celestron no longer makes that mount -- they came out with the Advanced VX mount as a replacement product). The CG-5 wasn't adequate so I sold it and bought what *should* have been a slightly nicer mount... which was also inadequate. I was about to buy a 3rd mount in the $1500 price range and enough other people told me to stop screwing around trying to find the cheapest mount possible and being disappointed... get a REAL mount. So I ended up spending about $3300 on the go-to version of a Losmandy G11 mount (a dream to use... I love this mount.) I don't own the Celestron Advanced VX mount (often abbreviated as just the "AVX" mount) but I understand some imagers complain that it has issues with stiction -- it doesn't have sufficiently good bearing to do a smooth job imaging.

This is composed of a lot of 8-minute sub-exposures captured via that mount using a TeleVue NP101is (101mm aperture / 540mm focal length apochromatic refractor (quad element)). But the main point about this image is that (there's a longer story as to "why") this was captured with no guiding at all. The mount performs well enough to handle 8-minute unguided exposures (assuming a good polar alignment is achieved).

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Telescopes & Auto-guiding:

As you increase the size and focal length of the telescope, things continue to get more difficult. Before I get into the mechanical challenges, there are also some challenges with the tight angle of view.

In the image above, the galaxy (M31 / Andromeda) is roughly 3º from edge to edge. But in the 540mm focal length scope using a camera with an APS-C size sensor, the entire thing is easily captured in one frame.

But I also have a larger scope with focal length of around 3500mm. The same camera on that scope has an angle of view of only about 22 arc-minutes wide. That means it isn't nearly wide enough to capture this object (but works nicely for much smaller objects). If you wanted to capture this object with such a rig, you'd have to take lots of panels that you stitch together. That might sound like no big deal... until you start thinking about all the steps. When stitching, it's nice to have an overlap of roughly 1/3rd of the frame. So now each frame is giving me roughly 1/4º wide (instead of 1/3º wide). To capture an object that is 3º wide, suddenly I need probably 12 images wide but probably at least 4 images tall... so we're probably looking at a minimum of 48 panels. Each section needs a couple of hours worth of data. So that's about 96 hours worth of image capture. Clearly that's well beyond what you capture in just one night. You don't want to capture any object when it's too low in the sky (preferably it should 30º or higher above the horizon). You can maybe capture around 4-6 hours of data per night. You could conceivably need 16-24 nights. And of course you don't want to image with the moon out. And you can't image with clouds in the way. You could easily end up spending a few seasons capturing jut one object. So there is a very practical reason why bigger isn't necessarily better.

And then there's the mechanical side to things. Flexure becomes an issue. Having a separate guide scope & camera can become an issue ... literally the extra weight of the main scope can cause it to flex slightly and it's notion of movement will be different from that of the guide scope & camera. So the correction made by the guider isn't accurate for the main imaging camera. So an alternative is to use the main scope for BOTH guiding and imaging at the same time.

You have to add up the weight of absolutely everything needed to image... the scope is the obvious one, but people often forget to add in the weight of the mounting rings, then there's the guide camera and it's mounting rings (and if you're going to piggy back vs. use a side-by-side mounting). Then add the weight of the main imaging camera as well as the weight of the guide camera. Some imagers use filter wheels (although that's more typical of monochrome CCD cameras and generally not used with color DSLR cameras) -- so that weight would need to be factored in as well. If there are finder scopes, etc. it all has to be added up.

The manufacturers will claim some weight bearing capacity of the mount. But there's no industry standard test for how they come up with that weight and it's rather subjective. When things get subjective and there are marketing & sales people involved... things get exaggerated (or at least stated in their most generous terms under the most ideal conditions). This means the weight bearing capacity of the mounts probably isn't realistic for use when doing "imaging". So most imagers tend to suggest that you should try to keep the weight to around 50-60% of whatever the manufacturer's stated capacity is.

And that was the challenge I had when I tried to do the academic exercise of specing out a $2000 imaging rig. I did use a Celestron AVX mount, a fairly light weight Newtonian astrograph as the scope. With minimal gear (just the scope, guide camera, and mounting rings) I was already pushing the limits of what an AVX mount can handle -- suggesting that I'd probably have some difficulties getting to guide accurately.

If I were trying to buy an imaging scope on a budget, I'd probably look at a Newtonian "Astrograph" type design. The "astrograph" simply means the mirrors on the scope are spaced to be able to bring an image to accurate focus when using a DSLR (a traditional Newtonian design won't focus when using a DSLR camera because the focal plane is too far away from the scope -- the reflex mirror on a DSLR means the image sensor is mounted nearly 2" farther back from the camera's mounting point and that's too far away for most Newtonian scopes.)

But the reason a Newtonian astrograph is attractive is because they're typically low focal ratio scopes -- so they capture a lot of light in a short amount of time. These scope are typically around f/4. An SCT (schmidt cassegrain telescope) is typically f/10. That's about 2.7 to 2.8 photographic stops slower. That means the f/10 scope needs to keep the camera shutter open for about 12 seconds per every 1 second that an f/4 scope would need. You can see there's a huge advantage to lower focal ratio scopes when imaging.

The bottom line is... if the $1k budget was an arbitrary value but you could actually afford to spend $3k... then I'd change the budget to $3k and ironically this will actually SAVE you money (I bought a lot of stuff that I had to re-buy because it was inadequate. I'd have saved money to just buy the right gear from the start instead of trying to skimp my way in to a very expensive hobby.)

But if the $1k budget is a realistic cap... then get a tracking head for a photo tripod and take "wide field" images uses camera lenses (a 200mm focal length is considered "wide field" in astrophotography.)

The iOptron used to be the most popular because it was the cheapest (by far). That lasted until Sky Watcher came out with a significantly better tracker that only cost slightly more money and the improvements were more than worth the extra cost. That pushed iOptron to redesign their head and now they have a newer model... but I haven't seen any good comparisons yet.

If you'd rather have a scope and you can increase your budget, I'm happy to suggest some gear ... a Newtonian astrograph optical tube is about $500. A decent mount is about $1500 (at the low end). An inexpensive guide scope & guide camera is probably another $500. There's probably some miscellaneous accessories such as mounting rings and adaptors. You quickly get to the $2500... 3000 range. The mount tends to be the most expensive component... but also the most important component.



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dashotgun
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The Tar Heel state
May 11, 2017 12:32 as a reply to TCampbell's post |  #4

this is all an eye opener in terms of the expense of getting into a new hobby. I know what you all mean when you say by once cry once. I could advance my budget but I am not sure at this point I am into this part of the hobby enough to spend 3000 plus dollars. This negates the buy once cry once philosophy. It is a conundrum.


You don't take a photograph, you make it. ~Ansel Adams
http://Davidsdigitalvi​sion.zenfolio.comexternal link

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TCampbell
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Joined Apr 2012
May 11, 2017 13:32 |  #5

dashotgun wrote in post #18352017 (external link)
this is all an eye opener in terms of the expense of getting into a new hobby. I know what you all mean when you say by once cry once. I could advance my budget but I am not sure at this point I am into this part of the hobby enough to spend 3000 plus dollars. This negates the buy once cry once philosophy. It is a conundrum.

But a tracker is MUCH less expensive, easier to use, and doesn't require extra gear (it doesn't need a guide-scope & guide camera, etc.)

Another reason why I like this route isn't the expense... but because it reduces the number of new learning curves you have to overcome all at the same time.

It also doesn't require that you fuss as much over the accuracy of the setup. When you setup the mount, the mount's axis of rotation needs to be parallel to Earth's axis of rotation. You achieve that by using an alignment aid that comes with the mount to identify the position of the celestial pole and then aligning the mount to that spot in the sky. But no matter how careful you are, this will never be perfect. That means that as you track an object you would like to image, you might getting some drift over the duration of the entire exposure. But when you use low focal length lenses the error is so small that you can hardly notice it. When you use a very high focal length telescope it hardly takes any error at all before the stars aren't "round" anymore (which is why those more expensive setups require "auto-guiding").

This means the whole learning process is so much easier when you use camera lenses on a tracking head.

The process of how you collect the image frames and combine all the data to create a result is pretty much the same...so once you learn the process for combining the data, you'll have no trouble moving to a bigger mount later.




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Celestron
Cream of the Crop
8,409 posts
Gallery: 1 photo
Joined Jun 2007
Texas USA
May 11, 2017 15:49 |  #6

dashotgun wrote in post #18352017 (external link)
this is all an eye opener in terms of the expense of getting into a new hobby. I know what you all mean when you say by once cry once. I could advance my budget but I am not sure at this point I am into this part of the hobby enough to spend 3000 plus dollars. This negates the buy once cry once philosophy. It is a conundrum.


Not to mention the thousands of dollars you could spend getting the minimum best equipment , you also have to ask yourself are you physically able to move a lot of heavy equipment around everytime you want to change locations and how well is your attention span at staying with a hobby that keeps you up into the late hours of night and sometimes up into the wee hours of morning without having your spouse upset because your not in bed sleeping (that is if your married) ? If not it's a great hobby to be in if you don't need much sleep . But even if you get in on the bottom totem pole of astronomy and you stay with it I can just about promise you over the next 5-10 years you'll invest another 2k or more into this hobby . It always happens , little here , little there , little this , little that , need an upgrade ... etc. If you have an open pocket book , nothing to worry about . If you don't , set your limit and stay with it , you'll be glad you did . I started out with a thousand $$ setup back in 97' . Last piece I bought 5 yrs ago put me a little over 3k total and I still don't have top of the line equipment . Now that i'm retiring from astro hobby , i'm not buying anything . I like getting to bed at a decent time and my pocket book likes me a lot more ;) .




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truecolors
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Joined Aug 2008
New Mexico
Dec 06, 2017 01:28 as a reply to TCampbell's post |  #7

This is a lot of excellent information. You have answered so many questions that I have had for such a long time.
I have been wanting to buy new equipment for years now, but have been overwhelmed and didn't want to make another costly
mistake. Thank you for taking the time to put this info out there for beginners such as myself. I really appreciate this.


Sheron
Have some stuff, want more stuff, need a good eye.

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truecolors
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Joined Aug 2008
New Mexico
Dec 06, 2017 01:31 as a reply to Celestron's post |  #8

Thank you for all this excellent information and advice.


Sheron
Have some stuff, want more stuff, need a good eye.

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