Is A 8inch Ritchey Cretian ok For Imaging Small DSO's?

[wesdon1]

Hi all. Could anyone tell me please, is a 8" Ritchey Cretian 'scope ok for imaging small DSO's and Galaxies? One has come up for a brilliant price, and I'm literally hovering over the buy button, but I just wanted to see if anyone could shed light on whether It's worth buying specifically for it's long FL, for imaging small Galaxies and DSO's?

many Thanks in advance!

Wes.

[Albir phil]

Long fl will zoom in more on DSO, however long fl is more demanding regarding guiding, and the mount if you are thinking of imaging. Also you will have a smaller fov with larger galaxy. Taking all this into account and if it's a bargain 🤗

[wesdon1]

5 hours ago, Albir phil said:

Long fl will zoom in more on DSO, however long fl is more demanding regarding guiding, and the mount if you are thinking of imaging. Also you will have a smaller fov with larger galaxy. Taking all this into account and if it's a bargain 🤗

@Albir phil Hi and thanks for your advice. I purchased it a couple of hours ago, it only cost me £350 + postage! They're £899 new! 

Yes it's for imaging, and it will be mounted onto a SkyWatcher HEQ5 Pro so I think the guiding will be ok as long as I polar align perfectly. I have an iPolar electronic polar alignment device which gets me the most perfect PA possible. 

Also I'm looking forward to the Planets making an appearance again in the coming months so I'm going to be imaging those with it too.

Cheers! Wes.

[Albir phil]

5 hours ago, wesdon1 said:

@Albir phil Hi and thanks for your advice. I purchased it a couple of hours ago, it only cost me £350 + postage! They're £899 new! 

Yes it's for imaging, and it will be mounted onto a SkyWatcher HEQ5 Pro so I think the guiding will be ok as long as I polar align perfectly. I have an iPolar electronic polar alignment device which gets me the most perfect PA possible. 

Also I'm looking forward to the Planets making an appearance again in the coming months so I'm going to be imaging those with it too.

Cheers! Wes.

👍 Same mount as me, I use polemaster hope you get some great images I'm sure you will

[Paul M]

I'd say it's a good buy. Yeah life might be easy with them there wide field 60mm APO's but where's the adventure in following the imaging pack?🙈😁

I've got a 10" StellaLyra RC. It's a great scope and with an optional 0.8x reducer/field flattener, I can just fit the main/classical part of the M42 in an image frame.

So if it doesn't already have one you can see what's available. You then have two scopes in one.

And, don't give yourself a hard time over collimation. Unless you are a devout pixel peeper, it isn't too critical. The road to perfection will take over your life. Don't sweat it! 😀

[TiffsAndAstro]

15 hours ago, wesdon1 said:

@Albir phil Hi and thanks for your advice. I purchased it a couple of hours ago, it only cost me £350 + postage! They're £899 new! 

Yes it's for imaging, and it will be mounted onto a SkyWatcher HEQ5 Pro so I think the guiding will be ok as long as I polar align perfectly. I have an iPolar electronic polar alignment device which gets me the most perfect PA possible. 

Also I'm looking forward to the Planets making an appearance again in the coming months so I'm going to be imaging those with it too.

Cheers! Wes.

an rc is one of the scopes im possibly considering in the far future for galaxies and nebulas, so i'd be interested in seeing how you get on with it.

[wesdon1]

On 15/06/2024 at 10:25, TiffsAndAstro said:

an rc is one of the scopes im possibly considering in the far future for galaxies and nebulas, so i'd be interested in seeing how you get on with it.

@TiffsAndAstro Oh cool! Well as soon as I get a clear night I'll be imaging with it, and will post my results and thoughts on this thread for you to evaluate. I bought it for the extra FL, and the fact it doesn't suffer many of the abberations that other optical designs do. One item I will be buying though, as @Paul M helpfully suggested, is a reducer/corrector.

I also want to image the Planets as they start appearing again in the coming months.

Really excited to see how I get on! 

Regards, Wes.

[wesdon1]

On 15/06/2024 at 10:24, Paul M said:

I'd say it's a good buy. Yeah life might be easy with them there wide field 60mm APO's but where's the adventure in following the imaging pack?🙈😁

I've got a 10" StellaLyra RC. It's a great scope and with an optional 0.8x reducer/field flattener, I can just fit the main/classical part of the M42 in an image frame.

So if it doesn't already have one you can see what's available. You then have two scopes in one.

And, don't give yourself a hard time over collimation. Unless you are a devout pixel peeper, it isn't too critical. The road to perfection will take over your life. Don't sweat it! 😀

@Paul M Thanks for the great advice and suggestions Paul! I will indeed buy a reducer/corrector, I didn't even realise that was an option so you helped me out me out there, thanks! 

I am expecting to have teething issues with guiding due to long FL, but I'm pretty confident in my PA abilities nowadays so hopefully I'll get it guiding well. 

Regards, Wes.

[wesdon1]

On 14/06/2024 at 13:21, Albir phil said:

Long fl will zoom in more on DSO, however long fl is more demanding regarding guiding, and the mount if you are thinking of imaging. Also you will have a smaller fov with larger galaxy. Taking all this into account and if it's a bargain 🤗

@Albir phil Yes it was a bargain mate, only £350! It arrived today and the Mirrors look ace, the focuser is good, everything just how I'd hoped! 

Yes regarding mount and guiding, I have the SW HEQ5 Pro so weight wise I'll be ok. The guiding should be ok because I have learned how to PA very well nowadays, plus I now use the amazingly simple PA tool, namely the iPolar. It's an amazingly accurate and beginner friendly PA tool! So hopefully any guiding issues will be minimal!

Regards, Wes.

[CCD-Freak]

Glad you went for it.  The 8" RC is great for smaller objects like galaxies and planetary nebulae.

These images were made with a 6" RC and a non cooled ASI482MC camera on an iOptron GEM45 mount sitting on a Todmorden pier.

I used a reducer to get to F6 so that NGC253 would fit the view.  I am getting more interested in imaging galaxies since there are "billions and billions" of them out there.

 

Have fun !!  (^8

 

Edited June 18 by CCD-Freak

[wesdon1]

@CCD-Freak Hey Paul! My goodness you're images are utterly beautiful!! I'm both amazed and inspired after seeing the quality of your images, and you didn't even need a cooled camera to produce them!!?? 

Thanks Paul! I'm so happy I bought it, and the price was ace, just £350 + postage! ( they retail over here in the UK at £899-£949, around $1150 'US ) As you will know well Paul, this hobby is rarely inexpensive, so any savings are always very welcome! LOL.

Now all I need is a cloudless night sky, which over here in UK is rare occasion! LOL

Regards, Wes.

[wesdon1]

here it is mounted to my HEQ5 indoors.

[TiffsAndAstro]

47 minutes ago, wesdon1 said:

@TiffsAndAstro Oh cool! Well as soon as I get a clear night I'll be imaging with it, and will post my results and thoughts on this thread for you to evaluate. I bought it for the extra FL, and the fact it doesn't suffer many of the abberations that other optical designs do. One item I will be buying though, as @Paul M helpfully suggested, is a reducer/corrector.

I also want to image the Planets as they start appearing again in the coming months.

Really excited to see how I get on! 

Regards, Wes.

A really versatile scope really appeals but even cheapest 8" sct is 1300 plus another 300 for reducer plus maybe another 1000 for possible hyperstar.

350 for a nice used RC sounds like you stole it

[Paul M]

14 minutes ago, wesdon1 said:

here it is mounted to my HEQ5 indoors.

Very handsome it is too!

My 10"RC is just about at the limit of my old NE6 Pro mount, but not beyond it!  The guiding does surprise me by being both good and consistent. I was looking for a bigger mount but after a year of hopeless weather, I just can't justify it

My scope was last under the stars on the 17th of January. 

[wesdon1]

20 hours ago, Paul M said:

Very handsome it is too!

My 10"RC is just about at the limit of my old NE6 Pro mount, but not beyond it!  The guiding does surprise me by being both good and consistent. I was looking for a bigger mount but after a year of hopeless weather, I just can't justify it

My scope was last under the stars on the 17th of January. 

@Paul M Thanks Paul! She is a pretty thing! 

I almost bought a used NEQ6 myself a few months back, but I too decided I couldn't justify the cost because of the atrocious weather we have here in UK! I think my last outing was early January, and it wasn't even a "clear" night, I was constantly fighting with passing clouds! Drives me mad! lol. Those RC10's are very expensive, you're very lucky to have one mate! 

The weather is looking potentially good at the weekend so fingers crossed we'll all get a few hours cloudless skies this weekend!? ( although I have learned that you can't rely on forecasts 100%, it's literally a case of looking up and seeing if it's clear right before you venture outside! ☹️ )

Regards, Wes.

 

 

[ollypenrice]

I think you may be over-estimating the importance of PA for guiding. Get it right by all means, but I've never seen a strong correlation between better PA and better guiding. The periodic error is likely to be 20 arcsecs or more, which tends to swamp the corrections needed to fix PA drift. Good PA is important for unguided imaging, however.

What I would do next is work out your sampling rate in arcsecs per pixel. The real world best you're likely to get from the seeing will be around 1.3 arcsecs per pixel so, if you are sampling a long well below that, you might consider binning, stacking in super pixel or resampling the image downwards by an appropriate amount before post processing. This will give you a cleaner image with no loss of real detail.

If you use the ZWO ASI 224MC, for instance, it looks like you'll be sampling at just under 0.5 arcsecs per pixel. That is certainly oversampled and would require a guide RMS of about 0.25 arcsecs. In reality you'll be doing well to reach 0.5, so it would be hugely advantageous to accept this and bin accordingly.

Matching camera to optics is so important in this game.

Olly

[wesdon1]

3 minutes ago, ollypenrice said:

I think you may be over-estimating the importance of PA for guiding. Get it right by all means, but I've never seen a strong correlation between better PA and better guiding. The periodic error is likely to be 20 arcsecs or more, which tends to swamp the corrections needed to fix PA drift. Good PA is important for unguided imaging, however.

What I would do next is work out your sampling rate in arcsecs per pixel. The real world best you're likely to get from the seeing will be around 1.3 arcsecs per pixel so, if you are sampling a long well below that, you might consider binning, stacking in super pixel or resampling the image downwards by an appropriate amount before post processing. This will give you a cleaner image with no loss of real detail.

If you use the ZWO ASI 224MC, for instance, it looks like you'll be sampling at just under 0.5 arcsecs per pixel. That is certainly oversampled and would require a guide RMS of about 0.25 arcsecs. In reality you'll be doing well to reach 0.5, so it would be hugely advantageous to accept this and bin accordingly.

Matching camera to optics is so important in this game.

Olly

Hi Olly. Thank You for your great advice. It's really odd you giving me this advice about arc-sec per pixel because I was just reading up about that very subject 30 minutes ago! I use a modded DSLR for imaging, pixels are 4.29um, FL of iOptron 8" RC is 1624mm, so I'll check my arc-secs per pixel with an online calculator and determine the best binning setting etc. 

Regarding the guiding accuracy and PA correlation, thank you so much for advising me there, I always assumed guided subs required super perfect PA to get the lowest RMS scores!? But now you've explained it to me, it makes a lot of sense, thanks! If the optics of my Rc 'scope are too mismatched, I could save up for a suitable matching camera. Incidentally, I was already planning on buying my first dedicated Astro camera in a few weeks!

Many Thanks Ollie!

Regards, Wes.

[ollypenrice]

Looks like the Canon will give you about 1.2 which is very nice.

Dedidcated astro cameras are coming with smaller and smaller pixels so you may struggle to find a match, in which case using super pixel should sort you out.

Olly

[Doversole]

Congrats and welcome to the RC owners club!

Reducers work well on cameras with 4/3 sensors or less. With the Canon, I wouldn't advise. If you go for an astro camera like the ASI533, or the ASI294 then a reducer will be useful in increasing your field of view and reducing your F ratio.

Have you looked into guiding? Personnaly I use a Celestron OAG (big prism) with the ASI174mm (big sensor for a guide camera). I never had an issue.

[wesdon1]

2 hours ago, Doversole said:

Congrats and welcome to the RC owners club!

Reducers work well on cameras with 4/3 sensors or less. With the Canon, I wouldn't advise. If you go for an astro camera like the ASI533, or the ASI294 then a reducer will be useful in increasing your field of view and reducing your F ratio.

Have you looked into guiding? Personnaly I use a Celestron OAG (big prism) with the ASI174mm (big sensor for a guide camera). I never had an issue.

@Doversole Hi and thanks, I'm happy to finally own one! 

My goodness your images are incredible! Another member @CCD-Freak showed me some RC 'scope pics he produced with his smaller 6" RC and an uncooled ZWO 482MC camera and they were stunning! So I'm at least reassured that if done properly, I will be very happy with my astro-images with my new RC! I'm actually now going for a ZWO 482MC camera, just like what @CCD-Freak used, because it's only £299, and my funds are low after the RC purchase, so it's a perfect first dedicated astro camera in my humble opinion! 

Regarding guiding I'm going to have to make do with my 9x50 guide scope/ZWO 120MM for now until I can afford the OAG like you helpfully suggested. I just cannot wait to get clear weather, I'm itching to get this RC outside! 

Many Thanks for advice and suggestions!

Kind Regards, Wes.

 

[Doversole]

13 hours ago, wesdon1 said:

@Doversole Hi and thanks, I'm happy to finally own one! 

My goodness your images are incredible! Another member @CCD-Freak showed me some RC 'scope pics he produced with his smaller 6" RC and an uncooled ZWO 482MC camera and they were stunning! So I'm at least reassured that if done properly, I will be very happy with my astro-images with my new RC! I'm actually now going for a ZWO 482MC camera, just like what @CCD-Freak used, because it's only £299, and my funds are low after the RC purchase, so it's a perfect first dedicated astro camera in my humble opinion! 

Regarding guiding I'm going to have to make do with my 9x50 guide scope/ZWO 120MM for now until I can afford the OAG like you helpfully suggested. I just cannot wait to get clear weather, I'm itching to get this RC outside! 

Many Thanks for advice and suggestions!

Kind Regards, Wes.

 

I would highly recommend you just start with your DSLR. It will give you a much better FOV (yellow assuming your DSLR has an APS-C sensor).

You will really struggle with the tiny FOV you will get with your ASI482MC.

[Clarkey]

I have been using an RC8 as my main DSO scope for some time. It will be pushing the HEQ5 - but it will do it. I have used it on mine, but it is better on the AZ-EQ6. I used to use a reducer/flattener - but now I tend to bin the data instead as I have othe4r options for wider FOV. Personally, I think they are underrated scopes - most people run a mile due to the potential collimation issues. 

Here a couple of mine:

 

[wesdon1]

On 20/06/2024 at 13:40, Clarkey said:

I have been using an RC8 as my main DSO scope for some time. It will be pushing the HEQ5 - but it will do it. I have used it on mine, but it is better on the AZ-EQ6. I used to use a reducer/flattener - but now I tend to bin the data instead as I have othe4r options for wider FOV. Personally, I think they are underrated scopes - most people run a mile due to the potential collimation issues. 

Here a couple of mine:

 

Thanks for the wise advice sir! Your images are breath-taking!! I would kill to that good at astrophotography!! 

[ollypenrice]

On 20/06/2024 at 14:40, Clarkey said:

I have been using an RC8 as my main DSO scope for some time. It will be pushing the HEQ5 - but it will do it. I have used it on mine, but it is better on the AZ-EQ6. I used to use a reducer/flattener - but now I tend to bin the data instead as I have othe4r options for wider FOV. Personally, I think they are underrated scopes - most people run a mile due to the potential collimation issues. 

Here a couple of mine:

 

These are certainly good images. No doubt about that.

Olly