Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Astrophotography and Sketching >> Beginning and Intermediate Imaging

Pages: 1
Jarrod
Pooh-Bah
*****

Reged: 01/20/13

Loc: SE USA
Celestron C6 or C8 for imaging?
      #5676975 - 02/13/13 02:52 AM

Thinking of getting one of these scopes on the new VX mount. I want to have my first "serious" scope to be something that:

a) Provides good visuals
b) Is good for imaging DSOs, the moon, and planets (priority in that order).
c) No more than $2k for scope and goto mount.

I considered a mounted newt, but realized that all the added weight would require a much sturdier and $$ mount, and would be much less convenient to move and store than a SCT. Someday I hope to add a 10-12" dob as a dedicated visual scope. In the meantime I need an all-rounder.

Obviously the bigger mirror can collect more light. But they are both f/10 or f/6.3 with a reducer. Does the difference impact astrophotography, such as the FOV you can get with prime focus? If so, which of these two is the better choice? What are the tradeoffs?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Fogboundturtle
professor emeritus


Reged: 05/20/09

Loc: Burnaby, BC
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5677343 - 02/13/13 10:08 AM

Quote:

Thinking of getting one of these scopes on the new VX mount. I want to have my first "serious" scope to be something that:

a) Provides good visuals
b) Is good for imaging DSOs, the moon, and planets (priority in that order).
c) No more than $2k for scope and goto mount.

I considered a mounted newt, but realized that all the added weight would require a much sturdier and $$ mount, and would be much less convenient to move and store than a SCT. Someday I hope to add a 10-12" dob as a dedicated visual scope. In the meantime I need an all-rounder.

Obviously the bigger mirror can collect more light. But they are both f/10 or f/6.3 with a reducer. Does the difference impact astrophotography, such as the FOV you can get with prime focus? If so, which of these two is the better choice? What are the tradeoffs?




If you want to image primarily DSO then SCT is a bad choice for you. You want a very wide refractor and yes the F ratio matters. The faster your scope is, the more light your camera will pick up.

It not that SCT are bad. Its they have this very long focal length to deal with. Even with a focal reducer, they require very accurate polar alignment and eternal guiding. This will frustrate most newcomer to imaging. most SCT have mirror shift don't have a flat plane unless you go with the more expensive SCT. Field curvator can vary a lot.

On the other hand, if you want to make Moon and planetary imaging your priority, then SCT are really your best choice. You need long focal length and you don't need perfect guiding.

take it from my experience. My first scope was an SCT 8". Like you, I had a goal to do DSO, I soon realize all the challenges I had to face. I kept my SCT and bought a Refractor to complement it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Celestron C6 or C8 for imaging? new [Re: Fogboundturtle]
      #5677382 - 02/13/13 10:36 AM

Jarrod...Take this advice from fogboundturtle if you really want to image DSO's. I have a 10" dob, 8" and 10" SCT, AT8IN imaging newt, and a few refractors. Even the 800mm focal length imaging newt was challenging for us as beginners. Once I bought my AT65EDQ the experience imaging was so much better. There really is no such thing as the perfect scope. For what the C8 would cost I think you could pick up something like the AT65EDQ ($599) for imaging and a nice dob for observing. Just my .02

Post Extras: Print Post   Remind Me!   Notify Moderator  
Stoverb
member


Reged: 11/08/12

Re: Celestron C6 or C8 for imaging? new [Re: rflinn68]
      #5677536 - 02/13/13 11:51 AM

I have a C6 and upgraded the mount to a GC5 so I can take images up to about 60 seconds at a time without too much problem. I really like my C6 because it's not too small but not too big that I can't move it around and use it. If your telescope is too heavy to move around, you aren't going to want to set it up all the time.

Any more than 60 seconds and I really see problems in the picture. I like how my C6 is light weight enough I can easily transport it to and from the site and don't have to worry about breaking my back every time. For true deep space stuff, most people want 3-5 minute (or longer) subs, so the equipment at this price range makes it more difficult.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jarrod
Pooh-Bah
*****

Reged: 01/20/13

Loc: SE USA
Re: Celestron C6 or C8 for imaging? new [Re: Stoverb]
      #5678597 - 02/13/13 11:38 PM

Quote:

For true deep space stuff, most people want 3-5 minute (or longer) subs




Why? In my line of work we routinely collect digital data with poor signal/noise ratios but overcome it by doing dozens of scans and summing them together. With N scans, the signal scales by a factor of N, while noise scales only as sqrt(N). So why not just collect 10*N 30-second exposures and sum them together instead of N 300 second exposures? What's the difference? You're either summing the data inside the camera, or inside the stacking software later....


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jarrod
Pooh-Bah
*****

Reged: 01/20/13

Loc: SE USA
Re: Celestron C6 or C8 for imaging? new [Re: Fogboundturtle]
      #5678620 - 02/13/13 11:53 PM

Quote:


If you want to image primarily DSO then SCT is a bad choice for you. You want a very wide refractor and yes the F ratio matters. The faster your scope is, the more light your camera will pick up.




Remember, I'm looking for a good all-around "one scope". I understand that there is no such thing as a perfect scope and I'm willing to make tradeoffs. I know that I won't get the big DSOs like Andromeda to fit in the FOV of an SCT. But there are plenty of others to look at and image that are much smaller. I've seen some more than adequate (to my untrained eye, anyway) photographs of smaller DSOs on the DSLR forum coming off C6 SCTs, for example. What's wrong with those?

I guess it comes down to what tradeoff I want to make. I could get a wide, short refractor for FOV/brightness (which lends itself to astro-imaging more), or go for a larger aperture SCT (which lends itself visual astronomy more). Am I thinking about that correctly?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jarrod
Pooh-Bah
*****

Reged: 01/20/13

Loc: SE USA
Re: Celestron C6 or C8 for imaging? new [Re: rflinn68]
      #5678629 - 02/14/13 12:04 AM

Quote:

Even the 800mm focal length imaging newt was challenging for us as beginners




What makes 800mm challenging? Imaging newts are like f/4, right? Shouldn't that be plenty fast and wide for imaging? I originally was leaning towards an f/4-f/5 8" or 10" newt on an EQ as a good all-around option. Ultimately the weight and overall encumbrance of such a package got me looking at the SCTs instead.

If I had a refractor as my "one-scope", I fear I'd be missing out on aperture for nice DSO visuals. Realistically I'll eventually end up with all three (SCT, Dob, ED refractor) so this really boils down to the question of which one to get first. If you had to live with *just one* telescope for, let's say a year, which would you choose and why?


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5678952 - 02/14/13 08:34 AM

Quote:

So why not just collect 10*N 30-second exposures and sum them together instead of N 300 second exposures? What's the difference?




The difference is you will want 10 (or more) 300 second exposures on a lot of objects to bring out the most detail.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5678962 - 02/14/13 08:41 AM

Quote:

What makes 800mm challenging?




The longer the focal length the more critical your polar alignment needs to be to avoid getting star trails. You want nice pinpoint stars. A short focal length refractor around 420mm is much easier to deal with when you are starting out.

Visual and imaging are really 2 totally different animals. I would decide which one you want to do first and buy a scope for that. A dob makes an excellent scope for visual use and you cant beat a small apochromatic refractor for entering into astrophotography, unless you want to use a camera lens.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jarrod
Pooh-Bah
*****

Reged: 01/20/13

Loc: SE USA
Re: Celestron C6 or C8 for imaging? new [Re: rflinn68]
      #5679008 - 02/14/13 09:26 AM

Quote:

The difference is you will want 10 (or more) 300 second exposures on a lot of objects to bring out the most detail.




I get that, but why not 100 30 second exposures instead? Tedium? The EOS software can bet setup to trigger the shutter ever ~30 seconds for infinity if you want (I've used it for time lapse before). I'm sure I'm missing a basic point, having never done astro imaging before.


Post Extras: Print Post   Remind Me!   Notify Moderator  
CounterWeight
Postmaster
*****

Reged: 10/05/08

Loc: Palo alto, CA.
Re: Celestron C6 or C8 for imaging? new [Re: rflinn68]
      #5679010 - 02/14/13 09:29 AM

Quote:

Why? In my line of work we routinely collect digital data with poor signal/noise ratios but overcome it by doing dozens of scans and summing them together. With N scans, the signal scales by a factor of N, while noise scales only as sqrt(N). So why not just collect 10*N 30-second exposures and sum them together instead of N 300 second exposures? What's the difference?




I think that already answered. IMO this is something best understood by doing. Imaging the double cluster in Perseus it won't matter as much as say trying to image Sh2-157(lobster claw) or IC443(jellyfish).

Using an SCt for imaging there is a lot to consider with respect to other options. For one thing, critical collimation is critial for imaging far more than visual, your eye will accomodate a lot of variance that on the chip would be unacceptable. Secondly, closed tube design of SCt's you'll also need to be conscious of optic acclimation and initially possible tube currents. If you can just leave set up outside this is somewhat minimized depending on temperature swings. Another consideration specific to the SCt design, (on some) unless you have an SCt where the mirror can remain 'fixed' (has mirror locks) you might encounter some movement and it's results on the image even if you are tracking well. The SCt is by no means a bad imaging optic, I just think there are better creatures out there. Ideally you want something where the only possible movment is from the focuser, and that only when you are trying to get critical focus - this especially true for imaging DSO's.

Imaging is more about the mount, visual is more about the aperture. Two different hobbies IMO.


Post Extras: Print Post   Remind Me!   Notify Moderator  
terry59
Post Laureate
*****

Reged: 07/18/11

Loc: Colorado, USA
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5679018 - 02/14/13 09:34 AM

Quote:

Quote:

The difference is you will want 10 (or more) 300 second exposures on a lot of objects to bring out the most detail.




I get that, but why not 100 30 second exposures instead? Tedium? The EOS software can bet setup to trigger the shutter ever ~30 seconds for infinity if you want (I've used it for time lapse before). I'm sure I'm missing a basic point, having never done astro imaging before.




If you want to read this thread, it may help.


Post Extras: Print Post   Remind Me!   Notify Moderator  
terry59
Post Laureate
*****

Reged: 07/18/11

Loc: Colorado, USA
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5679024 - 02/14/13 09:38 AM

Quote:

Quote:

Even the 800mm focal length imaging newt was challenging for us as beginners




What makes 800mm challenging? Imaging newts are like f/4, right? Shouldn't that be plenty fast and wide for imaging? I originally was leaning towards an f/4-f/5 8" or 10" newt on an EQ as a good all-around option. Ultimately the weight and overall encumbrance of such a package got me looking at the SCTs instead.

If I had a refractor as my "one-scope", I fear I'd be missing out on aperture for nice DSO visuals. Realistically I'll eventually end up with all three (SCT, Dob, ED refractor) so this really boils down to the question of which one to get first. If you had to live with *just one* telescope for, let's say a year, which would you choose and why?




One of the best SCT imagers I am aware of, Scott Rosen, spends time in the DSLR forum. I've seen him repeatedly discuss the difficulty of achieving focus across the image and things he does to compensate.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Fogboundturtle
professor emeritus


Reged: 05/20/09

Loc: Burnaby, BC
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5679135 - 02/14/13 10:37 AM

Quote:

Quote:


If you want to image primarily DSO then SCT is a bad choice for you. You want a very wide refractor and yes the F ratio matters. The faster your scope is, the more light your camera will pick up.




Remember, I'm looking for a good all-around "one scope". I understand that there is no such thing as a perfect scope and I'm willing to make tradeoffs. I know that I won't get the big DSOs like Andromeda to fit in the FOV of an SCT. But there are plenty of others to look at and image that are much smaller. I've seen some more than adequate (to my untrained eye, anyway) photographs of smaller DSOs on the DSLR forum coming off C6 SCTs, for example. What's wrong with those?

I guess it comes down to what tradeoff I want to make. I could get a wide, short refractor for FOV/brightness (which lends itself to astro-imaging more), or go for a larger aperture SCT (which lends itself visual astronomy more). Am I thinking about that correctly?




there is nothing wrong with an SCT for imaging. I think for a new comer to AP, its a much higher step to climb. Many have talk about mirror shift, collimation, tracking accuracy, slow F ratio, cooldown period etc...

Theses are all challenges that can be very overwhelming for someone starting out. I am fairly technical person. I work in the IT industry for over 20 years. Yet, even when I tested all my gear prior, you never know what might go wrong when you go imaging. You want to start simple and build up your skill from there.

I love my SCT, its a great scope and you can use an Focal Reducer to reduce the focal length and F ratio. My 8" with an F6.3 reduce is still 1200mm FL to deal with. You want ideally to start in the 400-600mm range.


Post Extras: Print Post   Remind Me!   Notify Moderator  
roc.ls1864
Pooh-Bah


Reged: 08/16/10

Loc: Blue Ridge Mtns. of Virginia.
Re: Celestron C6 or C8 for imaging? new [Re: Jarrod]
      #5679729 - 02/14/13 03:20 PM Attachment (48 downloads)

Jarrod - you can do imaginging with a C-8. I do it but found the addition of the f6.3 corrector/flattener helps a lot.
I also own faster refractors, it just depends on what you want to aim at.

I also have no guide system so I do a large amount of 30 second subs. Sure my images are not as great as others with better gear but all in all I am pleased and the C-8 is a good visual scope, which you seek too.

See attachment for an image with the C-8 and reducer, using 30 second subs.

One thing I've learned about AP for me at least is that the only way to see if something will work is to try it.Again, for me, that involves a lot of hit and miss but I guess if they were all perfect...where would the reward be when one comes out great?

I do think if starting over I may have gone with a used 80mm refractor, but the c-8 is by no means useless for AP.

My two cents only and worth what I charge, I imagine!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jesus Munoz
sage


Reged: 03/09/07

Loc: Querétaro, México
Re: Celestron C6 or C8 for imaging? new [Re: roc.ls1864]
      #5679949 - 02/14/13 05:50 PM

A C8 is better suited for visual and Lunar/planetary work, but it is a little harder to use in astrophoto, but it is not impossible to work with. Buy a 6.3 reducer (I think it is mandatory), and try it. The worst thing can happen is selling and buying some other stuff.

I've been using visually a Celestron 8 for 20 years and still very happy with it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Celestron C6 or C8 for imaging? new [Re: Jesus Munoz]
      #5680047 - 02/14/13 06:47 PM

The VX and a C8 would make a wonderful and very portable scope for visual. Get it and try it out, whats the worse that can happen? You'd have your visual scope then and you might be happy taking unguided 30 second subs. I have mine set up with a CG5 right now hoping to catch some photons. Clouds better stay north!!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Ugmul
super member


Reged: 05/17/11

Loc: Tucson AZ
Re: Celestron C6 or C8 for imaging? new [Re: rflinn68]
      #5684863 - 02/17/13 10:00 AM

I have lots of great photos with my Meade 8" SCT. but as others have said, the 6.3 FR is a must.

Also, for anyone looking to get into this hobby, and has access to a tablet of some sort, take a look at some software avaiable for astronomy. I use Skysafari Plus on my tablet, it allows me to adjust redicals for FoV's, and then you can see what will fit nicely with your scope on the screen before attempting to image with the scope.

What i descovered quick with both my Meade 8" SCT, and Newt, lots of the really big nebulas out there, really are BIG. But lots of stuff will frame in the 8" SCT w/6.3 FR.

Im still very much learning in this hobby, but here are a couple I like that I took with an 8" sct. Info can be found on the link.





I used the 8" a lot, but untill I could guide, getting high quality images was very hard, guiding is really importaint with this focal length.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Raginar
Post Laureate
*****

Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Celestron C6 or C8 for imaging? new [Re: Ugmul]
      #5685122 - 02/17/13 12:25 PM

Take a look at astrobin and search by equipment. You'll find pictures from each.

Personally, I really enjoyed imaging with a C5. It was light, compact, worked well with a focal reducer... everything you could ask for. I think it's native focal length was like 1250mm and with the f/6.3 reducer I got it around 900mm. Good image scale and it road on my CGEM like a champ.

You can image with anything Just depends on the amount of work you want to put into it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1


Extra information
3 registered and 19 anonymous users are browsing this forum.

Moderator:  Knuklhdastrnmr, fishonkevin, WOBentley, rflinn68 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 1258

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics