Scope question

BC · #1 20-06-2011, 08:35 AM

Hi,

I’m considering getting into some photography now that I have a Canon 500D and an EQ6 Pro mount. I really don’t think my 10” GSO Newt is mounted strongly enough for photography, so I’m wondering how to approach this.
- Buy stronger mounting (eg ADM) and modify the newt tube (not thrilled about cutting the tube)
- Buy some other dedicated scope

People/books tend to speak of prime focus as the preferred option, so my question is this – won’t going prime focus lock me into only one FOV for photography? Doesn’t this mean I can only shoot some things and not others? Do people have different scopes for different objects? Is there an F-ratio that is considered a reasonable balance – ie reasonable lunar shot and some DSOs?

Options I have considered:
- ED80 – only wide field
- ED100 – narrower FOV
- SCT with focal reducer – 2 FOV options

Interested in people’s thoughts,
Bruce

mswhin63 (Malcolm) · #2 20-06-2011, 08:42 AM

In a nut-shell yes, although the use of Barlows and Powermates and other lens other than visual lenses could be incorporated to increase magnification.

I am just starting and will develop my equipment base as i go. First I have the 80mm, then will add to these as I go. My next step will be an SCT I think or may go for Astrograph seeing I had good success with my DOB.

ZeroID (Brent) · #3 20-06-2011, 09:47 AM

I'm busy rebuilding my 10" to be mountable to an EQ6 but I did shorten it up in it's current Dob configuration to do prime focus DSLR photography. Mine was easy in that it uses struts so I just altered the top mount positions to lower the UTA by about 35mm.

But you're right, it does change the focal length and I am having to use an extender for some EPs to regain the focal length back. I actually use my 2x barlow with the lens unscrewed. I very rarely use it as a barlow anyway and I get twice the value

The rebuild is a Serrurier Truss design for lightness and it will be setup for Astrophotography focal length so I will have to still use an extender for some visual work. I still like looking at things as well.

BC · #4 21-06-2011, 05:30 PM

Thanks for the responses guys. I wonder if someone might be able to give a bit of an example of what sort of objects you'd aim for with different f-ratios. Is this impacted by the type of camera? Sorry if that's a seriously photo-newby question.

Thanks,
Bruce

mswhin63 (Malcolm) · #5 21-06-2011, 05:57 PM

This is 1500mm FL - http://www.waelect.com.au/mswhin63/D...11_17_30PC.jpg

This is about 50mm - http://www.waelect.com.au/mswhin63/W... DSS Final.png should label them, getting confused.

This is 1500mm from a DOB - http://www.waelect.com.au/mswhin63/M...2010_09_25.png

1500mm with a webcam -http://www.waelect.com.au/mswhin63/Jupiter/index.html#Jupiter 17_11_2010 No Barlow.jpg

I have done any 480mm FL shots yet.

Alchemy (Clive) · #6 21-06-2011, 08:09 PM

Couple of thoughts...

You can do imaging with the 10 inch, the mount will carry it. The limiting factor will be the stability of the scope tube, however as a beginner you will have lots of room to improve before you get too picky.

Unguided shots on the brighter targets, m8, m45, eta carinae. Will produce pleasing results for your first efforts. Guiding will become the next hurdle, personally for biggish newts I think an off axis guider is the best cheap way to go.

IF you were starting out from scratch, I would go an ed80, the wider field is more forgiving, plus there's not much fussing around with a refractor.

For now, just jump in and have fun.

mswhin63 (Malcolm) · #7 22-06-2011, 01:21 AM

I would recommend wide-field 80mm first too. For visual though aperture rules first off. Hard to choose.

gbeal · #8 22-06-2011, 07:03 AM

Short refractor gets my vote as well.
I have an NEQ6, same/similar mount as you. I also use n this mount a 10" f5 newt, albeit it is in a C/F tube, but the mount handles it OK. I have used a separate guide-scope, plus an OAG, with the OAG being "better".
But if you are starting out I reckon not to complicate things too much, so the refractor is simpler and easier to operate. In my case a 100mm or so, with flattener, and then get a flattener/reducer. I use an ED102 (612 focal length) and additionally reduce this with an 0.8x reducer, so get just under 500mm as well from the same scope.
Gary

Stu Ward · #9 22-06-2011, 07:08 AM

I'd see what you can get with your 10" first before spending money on anything.
I dont think you necessarily need to cut the tube or move the mirror either really do you ? Is it just that you cannot achieve focus on the camera ?
Might a lower profile focusser work ?
Cheaper alternative to explore first for sure

Stu

Alchemy (Clive) · #10 22-06-2011, 07:14 AM

You will need a field flattener for the newt, MPCC is the way to go, this will actually bring the focal point out a bit for you.... With luck that plus a low profile focuser will mean no tube cutting.

Again this is to be functional .... The whole setup has some limitations.

BC · #11 22-06-2011, 08:36 AM

Folks,

Thanks so much for the variety of contributions, especially those samples Malcolm. This array of suggestions is very helpful and I will ponder on this. I hadn't really considered the non-tube cutting options, so I will probably try that first. Thanks again.

Bruce

mswhin63 (Malcolm) · #12 22-06-2011, 10:23 AM

I have decided to withdraw my sale of the DOB because the reminiscing of imagery was too much to sell it. So I would advise have a go at what you already have. I expect I will get a RC or the like as my next scope but am going to concentrate on getting a guide setup first for my 80mm.