Hypothetical future aperture fever

[Hemi]

Dear Members,

For a fixed observatory setup and purely visual use, can we debate the merits of a 14-16in dob vs a 14-16in sct, taking $$$ out of the equation?

I have a 925 sct and 102 apo. I like sitting down, don't fancy a step ladder (I'm short and have started sketching). I like sct's for their sealed nature, infrequent collimation, compact size (not weight!) etc.

Would love to hear your views. (Strange our language is! Hearing views not seeing them)

Thanks

[el_draco]

I've used both. If you are after purely visual and want to do sketching then it becomes much more a question of finding a target and tracking it accurately for long periods of time. I guess once a target is located, then you want to be in a reasonably comfortable position. In that regard, a refractor or SCT provides a smaller degree of movement of the eyepiece compared to a newt. If you use a goto DOB, or a Alt-Az goto SCT thats obviously less movement compared to an equatorial.

If you are after wide field, brighter views, then a short FL newt is better but a SCT offers better detail on planets and compact DSO's, aperture for aperture, though the distinction is not so straight forward. You can also get a focal reducer for SCT's which changes their performance significantly. So I guess its a case of what do you want to observe?... as always ;)

[Atmos]

Even taking the size out of the equation you can purely look at the dob vs sct and then figure it out from there.

A dob of that size is likely to be working at F/3.3 - F/5.5 where as SCT's generally fall into the F/8 - F/15 range. The Newtonian design has definite benefits with cooling to ambient but that can be controlled reasonably well in an observatory anyway.

A 14"-16" SCT can either come fork mounted or as an OTA on an Equatorial mount so it'll be GoTo regardless. There are a lot of 14"-16" manual/push-to & GoTo dobs on the market as well.

One big benefit of a dob is that you can replace the primary mirror with a custom job for better quality. As long as it has the same focal length it'll largely be a matter of pulling out the old and putting in the new.

I'd personally go for the dob.

[billdan]

There is a thread on the DIY section of Cloudy Nights, where a gentleman converted a C14 SCT to a desktop DOB. He used a 3rd flat mirror installed in the baffle tube to bring the image out the side just above the Primary.

This way you get sit-down viewing and a long focal length.

Cheers
Bill

[silv]

pure visual in an observatory? I'd go for the OTA which is most easily to get converted into a bino down the road.
Just imagine...

[clive milne]

Simple..

Something like a 16" (up to 25") Binocular Newtonian, or equivalent.
Hands down the best (type of) visual instrument you could reasonably own.

~period~

[skysurfer]

What is the difference between this 'diagonal' and the standard diagonal behind the rear (which is also a 3rd flat mirror) ?
I can imagine that yoy have your eye on the side rather than behind the scope. Not much difference.

[billdan]

What is the difference between this 'diagonal' and the standard diagonal behind the rear (which is also a 3rd flat mirror) ?
I can imagine that yoy have your eye on the side rather than behind the scope. Not much difference.

By having the diagonal in front of the Primary you move the focal point a lot further out the side. A conventional diagonal at the rear of the OTA will not extend the focal point far enough. This would cause issues when the scope is pointing near vertical, you won't be able to get your head underneath.

[silv]

attach a camera and look on your tablet?



*dreamy sigh* yeahh