Wide and close N253

allan gould · #1 08-10-2011, 05:33 PM

Been experimenting with various scopes to see exactly what definition, guiding characteristics etc that I can achieve with my 5" Apo refractor and 10" SCT scopes. Each image is a stack of 6x10 min subs with the QSI583wsg camera at 1x1 binning, with just levels and curves with a touch of sharpening.
I've been trying to get the wsg component to work reliably with the SCT but really it only gives pinpoint stars for guiding with the refractor. I really only feel competent to guide at 2500mm Fl with a separate guidescope and guide camera with the SCT.
That said I'm happy with the detail and field flatness of both scopes and the next test is to use both with focal reducers/flatteners to see what they can do. But clouds ATM are a hinderance

Both images are full frame

mill (Martin) · #2 08-10-2011, 05:45 PM

I have been looking everywhere for N253 and can't find it anywhere

Just kidding

Personally i find the closeup looking much better with loads more detail.
For galaxies a long focal length is better.
The apo would be better suited for wide field work (unless you get a ED80

).

But as i said this is just me.
Martin.

Alchemy (Clive) · #3 08-10-2011, 08:13 PM

The detail in the 10 inch is clearly better,

Correct me if I'm wrong but I think you have a flt132 ?

Also if they are both same exposures the large is noticeably smoother in the background than the smaller... Any reason?

jase (Jason) · #4 08-10-2011, 08:21 PM

Impressive Allan. You've obtained exceptional detail with the 10". Some RGB data would be nice. You could perhaps shoot the RGB with the wide field instrument to complete both images. Resolution of the RGB data doesn't need to be that high when matching it to longer focal lengths. I have a few examples of this. Well done.

Lester · #5 08-10-2011, 08:29 PM

Nice views Allan. Love the detail you got with the 10" and the tracking is spot on. Interesting what you said about only being competant with a guide scope for tracking with the SCT. My experience is mirror flop happens and OAG is the only usefull way with my SCT. If you can get by with a guidescope, then by all means do that, as a OAG isn't as easy to use. All the best.

allan gould · #6 08-10-2011, 08:45 PM

Quote:

Originally Posted by mill

I have been looking everywhere for N253 and can't find it anywhere

Just kidding

Personally i find the closeup looking much better with loads more detail.
For galaxies a long focal length is better.
The apo would be better suited for wide field work (unless you get a ED80

).

But as i said this is just me.
Martin.

Thanks Martin for your comments

Quote:

Originally Posted by Alchemy

The detail in the 10 inch is clearly better,

Correct me if I'm wrong but I think you have a flt132 ?

Also if they are both same exposures the large is noticeably smoother in the background than the smaller... Any reason?

Detail in the 10" I expected to be better but the 10" is actually worse in the background for correction by flats than the 127mm as Ive been experimenting with various ADU values for my flats and light box with the QSI.

allan gould · #7 08-10-2011, 08:49 PM

Quote:

Originally Posted by Alchemy

The detail in the 10 inch is clearly better,

Correct me if I'm wrong but I think you have a flt132 ?

Also if they are both same exposures the large is noticeably smoother in the background than the smaller... Any reason?

Clive
Sorry its a 127mm apo. It was the second 127mm imported into Australia by Steve Massey for evaluation purposes and passed critical flat field and colour correction prior to purchase. No comment on the smoothness.

Quote:

Originally Posted by jase

Impressive Allan. You've obtained exceptional detail with the 10". Some RGB data would be nice. You could perhaps shoot the RGB with the wide field instrument to complete both images. Resolution of the RGB data doesn't need to be that high when matching it to longer focal lengths. I have a few examples of this. Well done.

Yes, Ive normally done this myself with a QHY8 camera but since I've sold that I will try to get some colour data for them both. Thanks for the comments, Jase.
I love the 10" as its a freak of a scope and Im currently comparing it to a 10" GSO RC for resolution.

allan gould · #8 08-10-2011, 08:56 PM

Quote:

Originally Posted by Lester

Nice views Allan. Love the detail you got with the 10" and the tracking is spot on. Interesting what you said about only being competant with a guide scope for tracking with the SCT. My experience is mirror flop happens and OAG is the only usefull way with my SCT. If you can get by with a guidescope, then by all means do that, as a OAG isn't as easy to use. All the best.

Lester,
I really don't have mirror flop with the SCT, or if I do its minimal. I use the fudged spring and bolt mirror lock on the Meade sometimes but its generally not necessary. I should post a set up of my guidescope at some stage as I spent a lot of time getting that right and finding all the small weak points in the train so that there is no flex at all. The only downside is that of added weight, thats why Im experimenting with the built it OAG of the QSI.
I agree OAG can be a pain but its the ideal situation to employ when it works and you have a "good" guidestar.

Hagar (Doug) · #9 08-10-2011, 09:09 PM

Very nice Allan. I think the level of detail in the two images lets the long focal length and larger appature shine ahead. With a luminance layer like this the colour composite should be breathtaking.
Interesting exercise. Makes me want a much bigger scope. You mongrell.

allan gould · #10 08-10-2011, 09:53 PM

Quote:

Originally Posted by Hagar

Very nice Allan. I think the level of detail in the two images lets the long focal length and larger appature shine ahead. With a luminance layer like this the colour composite should be breathtaking.
Interesting exercise. Makes me want a much bigger scope. You mongrell.

Bigger scope?!!!......... Ha
Want that QHY10, or else!!!!!!
That will get me the colour

Alchemy (Clive) · #11 09-10-2011, 12:09 AM

Thanks for the explanations, agree you could color up the large shot as it has great detail.

allan gould · #12 09-10-2011, 10:27 PM

Quote:

Originally Posted by Alchemy

Thanks for the explanations, agree you could color up the large shot as it has great detail.

Im making enquiries about a OSC tomorrow.

Paul Haese · #13 10-10-2011, 05:18 PM

Guiding at longer focal lengths can be quite challenging. Using the OAG is the right idea. Aggression and minor settings will get those stars round for you. I really like the longer focal length image myself and look forward to the colour version.

allan gould · #14 10-10-2011, 10:01 PM

Quote:

Originally Posted by Paul Haese

Guiding at longer focal lengths can be quite challenging. Using the OAG is the right idea. Aggression and minor settings will get those stars round for you. I really like the longer focal length image myself and look forward to the colour version.

I hear what you are saying Paul and you are correct but I'm really taking some time to fully investigate each aspect of my current scopes and setups with and without focal reducers. Then I will be getting down to some serious imaging but it's all a little moot as it will be from the suburbs, so the next will be narrow band.
Allan

strongmanmike (Michael) · #15 11-10-2011, 09:10 AM

These are good Allan, 253 lends itself well to showing some pretty specy details in good seeing

Mike

Ross G · #16 13-10-2011, 08:52 AM

Great galaxy photos Allan.

Sharp and so much detail.

Ross.