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Posts Made By: Ian Gibbs

July 7, 2003 02:49 PM Forum: Binoviewers

Fast Refractor

Posted By Ian Gibbs

Stuart
I've been using Siebert Black Night binoviewers with my AT1010 for a few days, mainly lunar and terrestrial so far. I bought these binos partly because they are a little lighter than most others, to minimise balance issues. These binos need the 1.8x OCA to reach focus in the AT1010 but otherwise they work fine in this scope optically. No problem merging images, no obvious chromatic effects, detail on lunar surface is still as sharp as you would expect with the Stellarvue. Especially with a 2" diagonal, balance on a camera/video-type tripod is an issue when the scope is tilted up over 20* or so, so I'm getting an adapter bar made to shift the centre of balance to compensate. The 2" diagonal gives a more secure hold for the binos than a 1.25".

Ian Gibbs

September 10, 2004 03:09 PM Forum: Equipment Talk

Refractor balance on Giro II with Binoviewer

Posted By Ian Gibbs

Three solutions I've used with success: (i) if you don't mind drilling holes in your dovetail bar, you can reposition the bar so that it sits higher on the tube rings (and the scope therefore sits lower on the mount; (ii) apply the same principle using a dovetail plate (drill holes in the plate to mount it lower on the Giro II arm); (iii) if you have or buy a dovetail plate with a flat bottom, you can attach a sliding weight system like ScopeStuff.com's to the bottom of the plate (again some drilling required). Advantage of the last solution is that you can also use it to balance the scope in the horizontal axis. Hope this is clear - let me know if not.
Regards
Ian

January 19, 2005 01:14 PM Forum: Equipment Talk

Unistar vs Giro vs

Posted By Ian Gibbs

Dave
I regularly use the Giro and Unistar, mainly with a C11. Both are good mounts. As you said, for grab and go the Unistar is more convenient because it doesn't use counterweights. The ability to quickly convert the Unistar dovetail holder from 2" to 3" using the exchangeable dovetail jaws can be useful too. When using DSC's I prefer the Giro because the scope/mount system can be balanced with counterweights, giving more accurate DSC readings. The Unistar is several inches taller than the Giro, which could be a plus or a minus for you.
Regards
Ian

February 9, 2005 04:30 AM Forum: Binoviewers

Bino resolution

Posted By Ian Gibbs

I was just looking at the Trapezium tonight, with a C11 and a pair of Nagler 16mm T5's in a binoviewer. For the first time in my short observing career so far, I could resolve the E and F stars with direct vision quite well, though they were both faint. I have mild astigmatism in both eyes, but don't wear glasses for observing. Both my eyes are 47 yrs old. I don't know the seeing scales, but I would say transparency and seeing were both "good". I have the feeling that if the seeing had been only a little less steady, I would have had trouble resolving them. A final tweak to get collimation dead-on certainly made it easier to resolve them, especially F.
Hope this is of some help.
Regards
Ian

April 6, 2008 10:46 PM Forum: APM

Maybe a new 6" ED below $ 5,000 from APM ??

Posted By Ian Gibbs

Markus

Do you know how the colour correction on this 6" ED f/7 would compare with the correction on the 180mm f/6 ED if the 180 ED was stopped down to 152mm (making it f/7.1)? In other words, would buying a 180 f/6 ED would also get me a 152 f/7.1 ED - two scopes for the price of one! smile

Ian Gibbs

June 10, 2008 04:34 PM Forum: Takahashi

Mewlon 180 & Feathertouch Focuser - Please Advise

Posted By Ian Gibbs

Hi Keith

I had this problem with my Mewlon 210, exacerbated by using binoviewers (in a diagonal) as well as a Moonlite focuser (which in contrast to another poster I am very happy with). My solution was to create more backfocus by moving the secondary mirror closer to the primary. Loosen the locknut holding the central set screw on which the secondary holder/mirror pivots, and then turn the set screw clockwise. (You'll need to loosen the 3 collimation screws first.) Turning the set screw clockwise will push the secondary holder/mirror toward the primary. If you need even more backfocus, you can purchase a longer M5 set screw (say 15mm or 16mm) to push the secondary even closer to the primary. That is what I did. I use Bob's Knobs which are long enough to still grip the secondary holder when backed out a few mm. I don't know about the stock collimation screws (I don't have them to hand). You can also move the primary a little closer to the secondary (same backfocus effect as moving the secondary toward the primary) but that is a little more difficult to explain and you mightn't need to do this if moving the secondary is enough. I haven't noticed any vignetting or other optical disadvantages by doing any of this, but I have plenty of back focus available now.

Regards
Ian