strange aberrations

[raymo]

I have been imaging for over 50 yrs, but always using reflectors or
SCTs; decided to try with my 80mm achro guidescope, and got these
strange aberrations.In the first sub the left side aberrations have lines
through them. I can only think that using the diagonal might be the
problem. Please disregard the star elongation; I was only playing around,
and didn't bother with accurate PA. I'm confident that someone will know
straight away what the problem is. Thank you in advance.
Rather than start a new thread about an old chestnut, I'll mention
another problem while I'm here. Since I updated my Synscan to 3.35
The scope hunts backwards and forwards every time it reaches a new
target. I remember other people having this problem, but can"t
remember what the outcome was back then.
raymo

[jr_simpson (Australia)]

Warp 1, 2 and 5 ???

[Jon (Jonathan)]

That's very odd, Raymo. I've been imaging a lot recently with my 80mm achro, with nothing like that.. Does the same thing happen with your guiding images?

[raymo]

Hi Jon, I only use the 80mm achro for manually guiding my wide
angle DSLR subs, so have only ever used it visually. Tonight I tried
it at prime focus without the diagonal; the weird shots were eyepiece
projection [24mm Koenig] with the diagonal. An example of tonight's
results is attached. I have to assume that the diagonal is the problem.
raymo

[doppler (Rick)]

More likely that it is the eyepiece causing the spherical aberations, a bad diagonal would not be as even.
Cheers Rick

[raymo]

It is actually a bit baffling Rick because I have been EP projecting with
this EP since I bought it in the early 80s. The University Optics
Koenig is a highly respected moderately wide angle EP, and was very expensive [$95 in Singapore] at the time. I'll try again with a variety of EPs and see what happens.
raymo

[cometcatcher (Kevin)]

I reckon it's the eyepiece also. With eyepiece projection you're only using the center part of the field. Edge distortion is present with most of them, Naglers being some of the best to correct it.

[raymo]

Why should this EP do this when it has worked fine with 6, 8, and 10"
Newts and an 8" SCT. Even if you are both right, what on earth are the
longtitudinal lines through the aberrations at the left of the first image?
{my guess is where the two mirrors meet inside the diagonal}. Also,
what are the crescent shaped lines at one end of the brighter aberrations
in the 3rd image?
raymo

[cometcatcher (Kevin)]

Diffraction patterns from objects in the optical path by the looks. One set looks like spider vanes?

[raymo]

A puzzle, isn't it. The 80mm achro, of course, doesn't have any
spider vanes. Hopefully tonight will show whether it is the EP or not.
The only object in the optical path was the diagonal.
raymo

[doppler (Rick)]

I use a 102mm f7 achro for imaging at times but I have never used the diagonal with the camera attached. I think that the less elements in the light path the better.

Rick

[raymo]

The only reason I used the diagonal is that my DSLR doesn't have a
moveable LCD screen, so that I would be required to perform contortions,
which at my age is just not on.
raymo

[doppler (Rick)]

I know what you mean, laying on the ground trying to focus etc. is not much fun. I have my achro mounted on a 8" gem newt. I focus the camera on something easy then use the newt as a guide scope. If I use the achro on its own I have a little 10" screen net book to use with live view.
ps its been about 30 years since I took my first image, 50mm f2.8 35mm film slr piggy backed on my 8" newt (yea I still have my first scope) and it took 5 min to get a reasonable image(single sub). Digital is so much easier to get started but a lot more complicated to master, lights darks bias stacking rgb etc. (stacking jpeg's is fine for me)
Rick

[raymo]

Hi Rick, I didn't get the chance to try other EPs last night, and tonight
doesn't look promising. My first astropic was well over 50 yrs ago,
60mm achro and Leica M3g, Fuji 1600, M42. I have decided to limit
myself to JPEGs and very limited processing, as I am struggling to
get my old head around Registax, DSS, Photoshop, Neatimage, and all
the other programmes ,.and processes within them. Plus, with the exception of a select few top imagers, the idea seems to be to produce images that are aesthetically pleasing to the imager, rather than
looking realistic. Some of the images you see look more like abstract
art.
raymo