janoskiss
31-12-2006, 12:22 AM
Some more on my new scope, after my initial impressions (http://www.iceinspace.com.au/forum/showthread.php?t=15838)... :)
Collimation
The primary is very easy to do with a Cheshire thanks to the big and smooth turning collimation and locking screws. With the locking screws done up, it holds collimation extremely well. Collimation was still Cheshire perfect after travelling 450km in the back seat of a car + 150km in the back of a van.
The secondary is trickier. It is only just big enough to catch all the light from the primary, so precise positioning and alignment is needed for getting the most out of the optics. This may be a turnoff for some beginners, but if it's too much hassle you can always just get the alingment right and put up with a little bit of "clipping" around the edge of the primary. By comparison, the GSO Dobs have oversized secondaries (at the expense of larger central obstruction), so are a lot more forgiving wrt positioning of the mirror.
The secondary alignment scews need to be done with an allen key unfortunately, but it stays put once it's done. The mirror is mounted on a black anodised metal piece and the collimation screws press firmly on that. No metal screws on soft plastic thankfully.
Star test
Now, I'm not v. experienced at this, but at 200x, star test looked textbook perfect to me. Inside and outside focus looked practically identical, with nice clean rings. At higher powers (using a barlow) the seeing made it more difficult to see what was going on. The inside focus rings looked fuzzier than outside, but I saw similar relative intensities between rings either side of focus.
Viewing
Unfortunately conditions have been appalling this past week, but from what I have seen so far I am very pleased with the scope.
The thing that seems most striking is that stars seem to be sharper than in my other two Dobs (the 8 and 12" GSO). And faint stars near bright ones seem to be easier to spot. Even in the poor seeing we had last night and tonight, I could see 6 stars in the trapezium at 80x, clear as a bell. I think the optics in this scope is very good. I am really looking forward to trying it out on Saturn and Jupiter in good seeing. :)
Just one night I was lucky to get about 15 minutes of clear skies between downpours at a dark location. M42 in Orion looked as good as I've ever seen it through any of my scopes. The texture in the gas clouds was very well defined.
I will have to do a side-by-side comparoo with my 8" GSO Dob one night. (I know 8 vs 10 is not fair but I'll do it anyway :P).
Eyepieces
The scope is an f/4.7, so expected to be tough on eyepieces.
It loves my 7 and 10mm Pentax XWs and 8.5mm XF, and does not mind the 20mm T5 Nagler either but that one shows some false colour and astigmatism near the edge of field. I can see coma from the mirror in the XWs, but it is very little by comparison. The 13mm Stratus does respectable job for what it costs, but certainly not sharp to the edge. But neither are the Panoptics, which have some seagulling near the edge (astigmatism, not coma). Aberrations seen near edge of field in Panoptic and Nagler practically disappear when barlowed (UO 2" 2x barlow).
I did not get a very good look through the 6mm Radian but it seems to do very well right across the field, with just a little colour near the edge. 15mm Antares Elite Plossl is excellent across 75% of the FOV, not so nice near the edge with astigmatism.
I did not try the silver-top plossls that came with the scope, or my HD orthos properly.
Other comments
Using the focuser at high power is a pain. Typical sticky grease/glue rack and pinion focuser issue. I haven't yet decided whether to regrease, shim and motorise it or try and fit the 10:1 GSO instead.
Mount could do with lighter touch in azimuth and smoother motion in altitude, but it is quite good for an unmodded setup straight out of the box.
I can carry the whole scope in one piece up/down flight of stairs to the to/from the back yard. :) It can be carried by the tensioner handles. Not quite as swish as the 8" GSO but not far off it either.
Collimation
The primary is very easy to do with a Cheshire thanks to the big and smooth turning collimation and locking screws. With the locking screws done up, it holds collimation extremely well. Collimation was still Cheshire perfect after travelling 450km in the back seat of a car + 150km in the back of a van.
The secondary is trickier. It is only just big enough to catch all the light from the primary, so precise positioning and alignment is needed for getting the most out of the optics. This may be a turnoff for some beginners, but if it's too much hassle you can always just get the alingment right and put up with a little bit of "clipping" around the edge of the primary. By comparison, the GSO Dobs have oversized secondaries (at the expense of larger central obstruction), so are a lot more forgiving wrt positioning of the mirror.
The secondary alignment scews need to be done with an allen key unfortunately, but it stays put once it's done. The mirror is mounted on a black anodised metal piece and the collimation screws press firmly on that. No metal screws on soft plastic thankfully.
Star test
Now, I'm not v. experienced at this, but at 200x, star test looked textbook perfect to me. Inside and outside focus looked practically identical, with nice clean rings. At higher powers (using a barlow) the seeing made it more difficult to see what was going on. The inside focus rings looked fuzzier than outside, but I saw similar relative intensities between rings either side of focus.
Viewing
Unfortunately conditions have been appalling this past week, but from what I have seen so far I am very pleased with the scope.
The thing that seems most striking is that stars seem to be sharper than in my other two Dobs (the 8 and 12" GSO). And faint stars near bright ones seem to be easier to spot. Even in the poor seeing we had last night and tonight, I could see 6 stars in the trapezium at 80x, clear as a bell. I think the optics in this scope is very good. I am really looking forward to trying it out on Saturn and Jupiter in good seeing. :)
Just one night I was lucky to get about 15 minutes of clear skies between downpours at a dark location. M42 in Orion looked as good as I've ever seen it through any of my scopes. The texture in the gas clouds was very well defined.
I will have to do a side-by-side comparoo with my 8" GSO Dob one night. (I know 8 vs 10 is not fair but I'll do it anyway :P).
Eyepieces
The scope is an f/4.7, so expected to be tough on eyepieces.
It loves my 7 and 10mm Pentax XWs and 8.5mm XF, and does not mind the 20mm T5 Nagler either but that one shows some false colour and astigmatism near the edge of field. I can see coma from the mirror in the XWs, but it is very little by comparison. The 13mm Stratus does respectable job for what it costs, but certainly not sharp to the edge. But neither are the Panoptics, which have some seagulling near the edge (astigmatism, not coma). Aberrations seen near edge of field in Panoptic and Nagler practically disappear when barlowed (UO 2" 2x barlow).
I did not get a very good look through the 6mm Radian but it seems to do very well right across the field, with just a little colour near the edge. 15mm Antares Elite Plossl is excellent across 75% of the FOV, not so nice near the edge with astigmatism.
I did not try the silver-top plossls that came with the scope, or my HD orthos properly.
Other comments
Using the focuser at high power is a pain. Typical sticky grease/glue rack and pinion focuser issue. I haven't yet decided whether to regrease, shim and motorise it or try and fit the 10:1 GSO instead.
Mount could do with lighter touch in azimuth and smoother motion in altitude, but it is quite good for an unmodded setup straight out of the box.
I can carry the whole scope in one piece up/down flight of stairs to the to/from the back yard. :) It can be carried by the tensioner handles. Not quite as swish as the 8" GSO but not far off it either.