Refractor for DSO photography or visual use

[BlueAstra]

I've noticed in a different thread some advice to buy a 80mm apo refractor for DSO photography (plus eq mounts + guider).This is because of the perceived higher contrast and image quality of the refractor.

I'm looking at where to go next for a telescope upgrade. In my current 114mm reflector, I can just see M13 (mag 5.7) as a sort of blur. I see lots of advice to go for the biggest aperture possible, so wouldn't a 80 or 120mm refractor give me a similar view visually as my 144mm reflector? I understand it may be a better platform for long exposure photography, but wouldn't I get the same or worse visual experience? I would like to improve the visual experience, but also add photography later.

[brianb]

Visually, even a 120mm refractior will show less than a 144mm reflector.

The reason small refractors are popular for imaging is that the short focal length plus the amount of adjustment in focusing makes it easy. Reflectors tend to have insufficient focal adjustment to get a DSLR to focus, and a long focal length makes the mount much more critical. Modern cameras are so sensitive that the aperture doesn't matter as much... for imaging, the mount is 90% of the trick and the scope only 10%; for visual work, the opposite is true.

IMO the best compromise is a small (6-8") SCT - on a altaz fork mount, great for visual work, also webcamming moon & planets; with a focal reducer on an equatorial mount (buy later) for DSO imaging.

[BlueAstra]

Thanks for the advice. My preferred route at the moment is almost as you suggest, but is a bit of a compromise. I've been toying with the idea of a cpc800 for visual + webcamming, perhaps adding a wedge later for photos. Thats because I need to minimise setup and setdown, and for the conveniance. However, the techie side of me says I should really do the proper thing and get a equ mount and 8" OTA. However, I have seen some decent photos from the cpc. My funds only allow one shot at this, so I'm taking some time to decide.

[brianb]

The alternative is to get the 8SE for visual & webcamming - the mount is not as good as the CPC but the tube is easily removed from the mount & then will fit any EQ mount with a standard Synta/Vixen dovetail. Deforking the CPC is probably a one-way operation.

The Celestron wedge is generally regarded as NBG but there are other options, including making your own.

There are people on this forum taking excellent deep space images with the CPC800 mounted on a wedge so it can be done....

[Milamber]

Hmm. Short focal length = smaller focal plane = harder to focus, not the other way around.

OP has a 114 not a 144, (I checked the sig) and it's a reflector (with central obstruction) wich would mean a 100mm refractor would be about equivalent.

True, the longer the FL the more critical the mount, but not that much until you start using barlows or if your camera has tiny (sub-5) pixels... in which case your modern camera wouldn't be so sensitive.

I agree witht e 90/10...10/90 statement though.

I would suggest that anyone buying a fork-mount scope for imaging should ensure their precious camera and associated attachments will actually fit through the fork once atttached to the scope. If you are short on funds right now, "borrow" the 90/10 rule from above and spend 90% of your budget on the mount, you can always stick with the 114 for now if necessary and witha decent EQ mount it may surprise you.

Arthur

[Psychobilly]

Good point about the kit passing through the mount Arthur...

There is just enough clearance for a DSLR to fit through the mount of the CPC when used with an f6.3 FR and the 55mm extension required and there's no room for anything else...

IIRC Thats one advantage of the CPC800 over the CPC925 which share the same mount...

Brians suggestion of going with the cheaper 8SE and getting an EQ mount is a good one you have the option of the Nexstar mount for convenience and the EQ for Astrophotography...

Peter...