Posts Made By: Tony L'Hotellier

For visual, the alt/az fork mount is much easier to get accurately aligned; once set up, you can be aligned and observing within a couple of minutes. The downside is that you have a much heavier piece of gear to carry.

Hi all, I've been thinking about why my ed100 star test looks the way it does, with well defined rings inside focus and fuzzy rings outside focus. I've seen a test indicating that the blue end of the spectrum is well corrected while the red end is less well corrected. So I've concluded that the outside rings are fuzzy because red is not focused to exactly the same point as green, while the inside rings are not fuzzy because blue is at the same focus point as green? I figure there are some refractor gurus here that can give me a tick or an E for effort?

Can someone please tell me whether I have this correct:

At best focus for white light, any refractor other than a full apo will have significant spherical aberration in one or more colors since you are effectively defocusing some wavelengths (the wavelengths that are not brought to the same focus as green). So even if a semi-apo has SA well controlled when focused for individual colors, there will still be spherochromatism present at best focus for white light.

Scopes down here are expensive though there are a few exceptions. Check out www.andrewscom.com.au They sell both GSO and Synta dobs at good prices.

Tony

AFAIK the WO is the same as the Proxima zoom from Hands on Optics. Brief review of Proxima at cloudynights: http://www.cloudynights.com/item.php?item_id=1221

Tony

That looks great Keith. I wish they came with factory installed cooling holes, though I'd prefer to have a fine filter material over the holes to keep bugs,etc out.

Televue offer a vast range of eyepiece types with differing characteristics. If you're thinking of buying a Televue eyepiece I find it easy to narrow down the list of candidates by eliminating the eyepieces that don't meet my needs. For instance, 12mm of eye relief is not enough for me in a 70 or 80 degree eyepiece, so the choices are narrowed considerably. You need to know what AFOV, eye relief, etc you like before spending a bunch of cash on the wrong eyepiece.

The Lunt zoom appears to be a Nikon spotting scope zoom (#7467) adapted for astronomy use. The Lunt zoom is competitively priced too considering it's quality.

Here are links to a couple of threads where Herr Rohr talks about recentering triplets. While he's doing this indoors it seems that you might be able to try making very small adjustments to the centre lens while obseving the coma on a real star. It's interesting reading anyway.


http://translate.googleusercontent.com/translate_c?hl=en&prev=/search%3Fq%3Dastro%2Bforen%26hl%3Den%26rls%3Dcom.microsoft:en-au:IE-SearchBox%26rlz%3D1I7ADRA_en%26prmd%3Dvdf&rurl=translate.google.com.au&sl=de&twu=1&u=http://www.astro-foren.de/showthread.php%3Fp%3D54500&usg=ALkJrhiRg1VxRsCL_FWfRPsDcnBU4_FPhA#post54500

http://translate.googleusercontent.com/translate_c?hl=en&prev=/search%3Fq%3Dastro%2Bforen%26hl%3Den%26rls%3Dcom.microsoft:en-au:IE-SearchBox%26rlz%3D1I7ADRA_en%26prmd%3Dvdf&rurl=translate.google.com.au&sl=de&twu=1&u=http://www.astro-foren.de/showthread.php%3Fp%3D41561&usg=ALkJrhj4lV1wH3rpKBURrEsNufdrau-cBg#post41561

In addition to the Casady saddle mentioned above, you could use a length of 2x4 to prop the CW shaft up in a horizontal position with counterweights already on - then you can sit the dovetail in the saddle, hold the OTA against your chest with one arm and tighten the saddle knobs with the other hand. I find this much easier than lifting above chest height.

You can drill a hole through the 2x4 to slip the CW shaft into to avoid the wood falling away while the tube is being mounted.