Scope recommendation

[Adrena1in]

Hi all, contemplating trading everything in and getting something "big". I'm thinking 10" to 14" and either a Newt, Truss Dobsonian, or SCT. Primary use is going to be for viewing the moon and planets, but also perhaps imaging these.

Part of me thinks a Newt or Dob might be better, as the lower focal ratio will mean I can still view some DSOs, whereas the high FR of the SCT might prevent this. Plus SCTs are generally that much more expensive.

But is an SCT that much better for Solar System objects?

Your views would be appreciated.

Thanks.

[Nighthound]

Having only owned SCTs, Newts and refractors, I can't compare Truss Dobs but have fiends that have large light buckets. While you gain in focal length with the reflectors, you loose contrast that the refractors offer.

I would suggest no smaller than a 10" SCT and no larger if you're setting up and tearing down each night. A large SCT(11" and up) isn't so bad as long as it's not mounted on a fork like the Meade units. The tubes themselves are not all that heavy. For imaging you'd want tracking so for that purpose the SCT is the logical choice. A Newt on an equatorial mount would work fine too. You'll just have to decide which focal length range you want, for solar system I'd go 2-3000mm and use a Toucam Pro.

How about a 10-12" free standing Dob to view with and an SCT to image with on the mount? That way you could be busy viewing while imaging with the SCT. No set up at all for the Dob so it's not a lot of extra work.

Of course reflectors mean you'll need to collimate but once learned it's a snap.

[Adrena1in]

Cheers Steve, but not sure I can afford both. ;)

I joined a site called AstroBuySell.com the other day, and straight away searched for items where I live. Found one seller shifting his Takahashi kit, including a Sky 90 for £950, (tempting), a TGM2 mount for £390, (very tempting), a few other bits, and a Mewlon 300 Reflector, which sounds incredible...but is over £7000!!! :eek:

[chris.bailey]

I personally would choose a refractor over any of them (think spending an age with colimation, tube currents, slow for imaging, cool down etc etc). My 8" SCT is a PITA but for purely visual and planetry it is good.

The SKY90 is lovely scope for imaging. A fair few W/O FLT 110's on the second hand market.

[Jaxdialation]

I think you are going to find that visual astronomy leads you to as much aperture as you can move and afford. That usually means a newtonian Dob since the $/inch is the best.

For imaging the scope is really _secondary_ the mount is of primary importance. The mount becomes less important at shorter focal lengths.

I'd strongly recommend that you read up on astro photography before making a move.
Ron Wodoski's "New CCD Astro photography" is the book to read.

AP is extremely demanding and expensive, you need to stack the odds of success in your favor early on so that you will stick with it. Read up.

[Adrena1in]

Thanks Jax. I've been imaging for a while now, and after about two years I'm really not getting anywhere, which is why I'm thinking of moving mainly to visual with some imaging of solar system objects. Had my eyes on an 11" SCT, (Celestron C11), for under a grand, but think that purchase has fallen through.

I'll wait until I'm sure I've lost it, then perhaps look at a SkyWatcher FlexTube. Easy to handle, and a 10" or 12" should be relatively cheap and give good views.

[Jeff]

Have you looked into Mak-Cassigrains if your primary interest is planetary & the moon? I've heard those are the sharpest & have a longer focal length than SCT's. They're doggie for DSO's though. A 10-11" SCT is pretty easy to set up and break down too though and does a great job in a lot of areas.

[cspratt]

Try and get yours hands on the Celestron 9.25" SCT either just an OTA or complete setup. Optically very good on planets, and with an F/6.3 or F/5 focal reducer does a good job on DSOs. The OTA is about 20 pounds. The optics are far superior to the 8, 10, or 11 SCTs now on the market. A Mak-Cass. is good but most long focal lengths so you don't get the view on DSOs.

In the good old days a refractor used for planet studies had a focal length of f/15-20. Comet hunters like the late Leslie Peltier (U.S.) used a "Comet Hunter" which was a well used 6" f/8 refractor. In his book "Starlight Nights" he admitted it was lousy on the planets. (Great book by the way well worth reading).

Bill Bradfield in Australia primarily uses a 6" f/5.5 refractor on an alt-azimuth type mount. I doubt he uses this for anything but comets but has bagged about 18 or so comets over the last 30 years.

Apart from a good OTA you will need a quality mount such as the Astro-Physics Mach1 or the Tak. GEMs. Personally I never regretted getting my 9.25" SCT . I mounted my OTA on an Astro-Physics 600E Goto GEM which is no longer produced. That mount will take 2 of my small refractors mounted side by side if I wish to do wide field work.

[Adrena1in]

I saw a Celestron 9.25" ST for sale the other day. (Well, I was after an 11" actually, and the seller told me he had another buyer, but *he* needed to shift his 9.25" first...never found out who that other chap was though.)

I've now found a Meade LX200 10" that I'm going to buy, hopefully, and I'm sure it'll be a good starting point into this sort of astronomy and astrophotography. With a FR I hope it'll allow me to occasionally shoot DSOs, but for the time being I'll try my hand at solar system imaging. I managed tiny images of Jupiter and Saturn using my 5" f/9.5 refractor, but I want to go bigger! ;)

Ta.

[chris.bailey]

10" LX200 is a nice scope, crater hopping on the moon is simply amazing. Darned heavy to lug around though.

[Nighthound]

I saw a Celestron 9.25" ST for sale the other day. (Well, I was after an 11" actually, and the seller told me he had another buyer, but *he* needed to shift his 9.25" first...never found out who that other chap was though.)

I've now found a Meade LX200 10" that I'm going to buy, hopefully, and I'm sure it'll be a good starting point into this sort of astronomy and astrophotography. With a FR I hope it'll allow me to occasionally shoot DSOs, but for the time being I'll try my hand at solar system imaging. I managed tiny images of Jupiter and Saturn using my 5" f/9.5 refractor, but I want to go bigger! ;)

Ta.

Tim, the LX200 is a fun scope. I wish I could have afforded to keep it for the tube but I needed to help fund my G-11 at the time. Get some Bob's Knobs for it if it doesn't already have them, they make collimation very easy. Also, you may want to consider a high quality barlow or better yet a TeleVue Powermate for planetary. The PMs aren't cheap but they're as good as it gets for magnification. A Toucam Pro webcam would be your best bet for planetary. You'll be able to stack 100s of exposures and resolve stunning detail.

Here are some shots from long ago taken with my 10" LX200 and 20D. The planets are single exposures so no where near what a good web cam can deliver. Don't be too hard on me for the processing, especially The Dumbell Neb, I was just getting started back then. :D

My favorite thing to do with the LX200 was to crank up the magnification on a steady night, turn the slew rate way down and do Apollo-like slow fly overs of the Moon. That would knock peoples socks off when I showed them. :) And globulars like M13 and double stars(especially Albireo) are beautiful in dark skies.

I hope you get the scope you're after.

http://i3.photobucket.com/albums/y67/Nighthd/Astrophotography/test/mars22x-1-1.jpg

http://i3.photobucket.com/albums/y67/Nighthd/PS%20Gallery/marspostr.jpg

http://i3.photobucket.com/albums/y67/Nighthd/PS%20Gallery/sombrerobcc.jpg

http://i3.photobucket.com/albums/y67/Nighthd/Astrophotography/test/sat052B-1.jpg

http://i3.photobucket.com/albums/y67/Nighthd/Astrophotography/test/m27new4.jpg

[Adrena1in]

Wow, those are great shots Steve, thanks. Planets are what I'm going to be aiming for to start with, and at some point, if I upgrade my mount, I'll perhaps head into Deep Space territory again. (Still not sold my APO, so maybe I'll find an excuse to hang onto it!)

I'll investigate the TeleVue PowerMate as well, cheers.

Tim.

[Jeff]

Tim, I love my 10" LX200 GPS. Even being alt/az it does well on DSO's with a focal reducer on it. Here's a link to a gallery of astro stuff I've done with it. http://************/nsqbfc

Planets are great visually but I haven't had a lot of success photographing them. (haven't really tried much though)

[Adrena1in]

Cheers Jeff. The LX200 I'm hoping to get my hands on is on a CG-5 mount. Not sure how well it'll handle it, but I'm sure I could scrape together enough for an EQ-6 or something one day.

By the way, I got a Trojan Virus alert when I tried to access your site!!

[Jeff]

By the way, I got a Trojan Virus alert when I tried to access your site!!

Were you using Google Chrome by chance? That seems to flag it because its on a hosting service. (hostdepartment.com) Not sure why. Thanks for the heads up though.

[Adrena1in]

No, I was using Firefox, but I also have a free Anti-Virus guard from Avast!, and it was that that was flagging the site I think.

[Adrena1in]

...I needed to help fund my G-11 at the time.

I've just seen a G-11 for sale too, for "only" £1000. Man, that's tempting!

[spit]

i seen an f/5 reducer mentioned earlier in this thread for a 9.25 SCT-- what kind of reducer is this?

[Adrena1in]

Meade do 6.3 and 3.3 focal reducers, which (I think) reduce an SCT focal length to 63% and 33% respectively of the original focal length. I've got a cheap generic 0.5x Focal Reducer, which I gather cuts a focal length by 50%, but never successfully used it. It's just an extra "lens" that screws somewhere into the image train. Don't really understand how they work myself. I see a prime focus image as being the widest field of view the telescope can physically show, due to the limitations of the tube. How you can somehow widen that field and reduce the focal length by adding a lens is beyond me!

[MintMark]

I think the idea is that with your camera/ccd at prime focus the image circle from the telescope is (often) larger than the sensor, so you only capture a portion of the field of view.

The focal reducer makes the image circle smaller so the sensor captures more of it and the resulting image has a larger firld of view. I suppose this only works if the sensor is smaller than the image circle to start with.

[Adrena1in]

I see...that does make sense! I'm now wondering how I can find out how large the image circle of a scope is. Say I get the Celestron C11 I've got my eyes on, and want to get a 6.3 or 3.3 FR...would the 3.3 work I wonder, and would I really be losing potentially 67% of the field of view the scope can actually display!?

[Jeff]

Tim, I think I read somewhere that the f/3.3 reducers are meant only for the smaller chip CCD cameras and not the DSLR's. My f/6.3 works great though on the 10"

Ah, here's one article I found on it:
http://assne.org/board/viewtopic.php?t=1786

[MintMark]

I see...that does make sense! I'm now wondering how I can find out how large the image circle of a scope is. Say I get the Celestron C11 I've got my eyes on, and want to get a 6.3 or 3.3 FR...would the 3.3 work I wonder, and would I really be losing potentially 67% of the field of view the scope can actually display!?

Is it as simple as the size of your camera sensor compared to the size of the eyepiece the telescope uses? It can't be that simple can it?

[Adrena1in]

Looks like my purchase of the Meade 10" LX200 has fallen through...seller's gone away for a few months I think. But I have a Celestron C11 XLT lined up, which should do nicely!! :) :) :)

[Jaxdialation]

This han't been my experience. Most of my scopes have had image circles
in line with my camera. It is really easy to figure on how a camera matches up with a scope. Here is a link to some free software which includes sample deep space images. You can alter all the variables affecting your _imaging system_.

http://www.newastro.com/book_new/camera_app.php

The issue with focal reducers is that the area of sky covered by each pixel of the camera INCREASES. Shorthand this is called acsec/pixel. And it is an important factor in get the camera to match the scope. Imaging area AND acsec/pixel

Hope this helps

I think the idea is that with your camera/ccd at prime focus the image circle from the telescope is (often) larger than the sensor, so you only capture a portion of the field of view.

The focal reducer makes the image circle smaller so the sensor captures more of it and the resulting image has a larger firld of view. I suppose this only works if the sensor is smaller than the image circle to start with.

[Adrena1in]

Well, I've got my scope...Celestron C11 XLT. It came with an attached Dovetail bar for the Celestron CGE mount, which I'm hoping will fit the Losmandy/Vixen Dual Saddle Plate I've got on order, (though what's happening with that I've no idea...better be here soon!)

[VIGER]

Hello

Correct me if I am wrong .... but the FR from Meade and Celestron were designed for a 35mm camera and since distances are important thus for me to think that these focal reducer design should be revised? Unless you have a FF DSLR ?

[chris.bailey]

Hello

Correct me if I am wrong .... but the FR from Meade and Celestron were designed for a 35mm camera and since distances are important thus for me to think that these focal reducer design should be revised? Unless you have a FF DSLR ?

The important thing is the distance from the FR to the chip. Get this wrong and you will loose field flatness (eggy stars on the periphery). Most FR's are VERY sensitive to this distance. Nikon and Canon have different distances from the lens flange to the chip meaning you might have to add spacers. On my TAK setup I even have an adjustable spacer in the chain so as to get the spacing absolutely spot on.

[chris.bailey]

Hello

Correct me if I am wrong .... but the FR from Meade and Celestron were designed for a 35mm camera and since distances are important thus for me to think that these focal reducer design should be revised? Unless you have a FF DSLR ?

The important thing is the distance from the FR to the chip. Get this wrong and you will loose field flatness (eggy stars on the periphery). Most FR's are VERY sensitive to this distance. Nikon and Canon have different distances from the lens flange to the chip meaning you might have to add spacers. On my TAK setup I even have an adjustable spacer in the chain so as to get the spacing absolutely spot on.

[Adrena1in]

Have had my C11 and EQ6 ready to go for a few days now, finally getting my dew heater controller today. So apologies for the crap weather we've been having in the UK...it's all my fault. I SO can't wait to give this thing its first light. (Well, its first light with me anyway!)

http://img53.imageshack.us/img53/7043/c11sideclose.jpg

[SteveInNZ]

Very nice.

Dear Santa ........

Steve.

[chris.bailey]

Very nice indeedy. Are you planning on piggybacking on that to guide with ?

ps you are right about the cr&p weather. Only nice evening here has had a full moon to contend with :-(

[Adrena1in]

Are you planning on piggybacking on that to guide with ?

Yeah, probably. It's got an ADM rail on top, so should be very simple to get a couple of whajamacallits to enable me to mount either my WOZS70 or my ST80 on top.

Not sure how easy it's going to be to set up some sort of guiding on the EQ6 though. I need to read up on it because it doesn't have an Autoguider port like my EQ5 does.