Posts Made By: Oren Soffer

I need an aluminum dust cap for a dew shield with outside diameter of 8.125". Astrozap doesn't have such a thing. Does anybody know where can find one?

Thanks for your help!

oren.

Came accross this unusual spider last week in Hawaii. Does anybody know anything about it? (This macro image is only 30% of the original)

oren.

I have an old Celestron 10" f1.5 Camera that has no primary but it does have the front 10" round (optical flat?) glass window. Is that glass considered to be flat enough so I can glue a seconday in the middle and add a good 10" f/4 mirror and a focuser and have a reflector with no spider of a good quality? I know those cameras were made for low power imaging, so will it take high power ok with that glass in the way?

Thanks, oren.

I did not get any help on the refractors forum so I thought I should try here... I am at the final stages of putting together a tube for a 7" refractor lens I just bought. It is a triplet so I know it will take a little while for it to cool down, and to make things worse, I flocked the entire tube and baffles. Does the 0.03" thick velvet have a major impact on the thermal behavior of a sealed aluminum tube? The lens cell is flush with the counter-cell ring so no gap between them. Should I keep the tube sealed or maybe I should use the push/pull screws to create a small gap, say 1/16", to help the lens cool down faster?(lets ignore the dust issue for the moment). Will it make a major (good/bad) difference? More tube currents, less tube currents?

Thanks, oren.

I just picked up a used 8" f6 Achro lens on Amart knowing not to expect too much, based on the sellers description. I star-tested it tonight, it has some SA probably 1/3 to 1/2 wave but also astigmatism that really bothers me more then anything else. Retaining ring is loose so no problem there. It looks like someone already messed with it by taking it apart. Spacers seems to be there, but my question is: can astigmatism be reduced if I rotate the lenses in relative to eachother? I do not have an optical bench but will dive into the project if there is hope. Attached is a picture of the lens in the temporary tube from a different perspective...

Thank you!

oren.

I am looking for the darkest site possible up to 300 miles from Los Angeles to observe from later on this month. Was thinking about somewhere between Lake Isabella and Owens Lake by the 395 FWY, however any other area or direction is fine as long as it is noticeably darker then Mt. Pinos, and known to have good seeing most of the time. Any advise would be truly appreciated!

Thanks, oren.

Below is an image of a startest I did on an SCT that appears to have an optical defect. This tube apparently used to be excellent according to the owner but something happened to it. To me it looks like it has a pinched primary or secondary, a bad zone or turned edge, but it might be as simple as rotated corrector plate (wrong indexing). It's not mine so I can't take it apart but I can advise the owner. I need you experts to help me pinpoint the issue (and the star images... ). It is not thermal issue, the tube was outside at 60ºF for two hours prior to the test, I also flipped the tube upside down and the pattern flipped with it. I was using an artificial star only 65 feet away so please ignore the Spherical error, well, that and the dust on the eyepiece in the picture. No diagonal, just eyepiece and p&s camera. Real star shows the same defect. Collimation is very close but it is difficult to get it dead on because near focus not only the rings become square but the airy disk looks like it is broken to pieces. At perfect focus, the airy disk looks nice but lots of haze around it distributed unevenly. In and out focus might be flipped in this test, I'm not sure.

Thank you in advance for your help!

oren.

Hi all,

Anybody going to Pinos tonight or any other site in the area?

Oren.

Garry,

Happy to hear you like your PST and the sun co'operates. Sure was a good show today. You will find that the plossl will be better because it has less glass in it and only 4 elements. It's true for night-time an even more so for day-time. I have a full set of Naglers, few Radians and Panoptic (22mm), but nothing is as good as the TV Plossls (full set) and the C-Max line(I have the 18mm) for H-Alpha when it comes to contrast and (lack of) reflections.


oren.

Barry,

I have a stacked 40. When I remove one filter :S most of the pictures I see on the web are better then what I see through the eyepiece. When I put it back , I've seen *very* few pictures on the web that can match the view through the eyepiece. Last star-party I had my setup side by side with a single 60... I'm sure the owner of the single 60 upgraded by now. Infact, I don't see much difference between a single 40 to a single 60 anyway. The best part is that you can buy one on Astromart and a $6 adapter and find out for yourself. Don't like it? sell it for what you paid for it.

oren.