refractorholism and refractoritis.

[Stephen65]

I have a 5" APO, a 10" DK and a 20" dob under construction. All of them have their advantages and disadvantages. The views are not comparable but there is something uniquely pleasurable about the high contrast widefield views you get through a good quality APO. When I have it set up at star parties I always get people saying "oooo the stars are so sharp!".

Obviously if I was hunting some specific DSO or trying to make out festoons on Jupiter the 5" is not my choice of instrument, but for appreciating the aesthetic beauty of starfields and larger open clusters its hard to beat it (especially when used with an Ethos).

[NQLD_Newby]

Arpeturitus for me I'm afraid. Must be very contageous, as just last year I was fine.

[Stephen65]

In my humble opinion, if the mirror of a 10" f/5 dob is still spotlessly clean and freshly re-surfaced, it should perform more or less on par with a 6"-6.5" Apo in terms of light-gathering ability ONLY, the image quality will not be in the same league.

This isn't right. A 10" mirror gathers 2.37 times as much light as a 6.5" lens and even allowing for lower transmission off mirrors and the secondary obstruction the 10" is still going to be considerably superior in light-gathering.

As others have said a lot of comparisons people make refractor v reflector is expensive APO v generic Chinese reflector. If you get an equivalent quality reflector it's going to be a lot fairer comparison.

To give an illustration, my 10" Mewlon has two mirrors and is a pretty decent quality folded reflector. Once it is properly collimated and cooled, and provided the seeing is decent, it will absolutely crush my 5" APO on DSO's and planets. The difference on something like Eta Carina is like night and day, the Mewlon can deliver larger image scale and a much brighter image.

[Starkler (Geoff)]

Originally Posted by ausastronomer

When I am finished building it, I will happily let anyone throw their 6" refractor of any manufacture up against it.

Actually John to be fair, your challenge should be comparing your 10" newt against an 8" apo. You do however have the right to nominate the place for this showdown.

I cant imagine too many people willing to drag their 8" apo out to the middle of the field at a star party

[Wavytone]

A case of mild refractoritis.

I'm aiming to have three catadioptrics and two refractors on the same mount mid next year..

[Ian Robinson]

Originally Posted by Wavytone

A case of mild refractoritis.

I'm aiming to have three catadioptrics and two refractors on the same mount mid next year..

Don't set it up near any airports , I don't think the cops would be impressed.