KK Widescan III Wanted

[Ambermile]

Hi all

Looking for any of the above - there are four... the 30mm 2", the 20mm, 16mm and 16mm 1 1/4". I may have a 13mm here in the UK but if anyone has the others and can take Paypal (or trade maybe... got an 900NC here with IR block and 0.5 reducer and 1.25" adapter I could trade for a couple, or even there's a Philips Vesta SC1 maybe...)

Let me know what you have and a price...

Arthur

[Ambermile]

Well, I do have a 13mm now - any others out there?

Arthur

[Rodstar]

Arthur, don't you find that design of EP shows hideous coma with your fast mirror?

[Ambermile]

Well, my mirror is rather a good one actually Rod - thanks to Jim Vincent here in the UK. Once the drives and so on are installed I should be able to maximise the time an object is actually in the middle of the FOV rather than constantly trying to keep it there manually. So, not being able to get on with Naglers I am looking for other widefield options and the KK EP's have a rather good reputation. OK, outside 75% or so of the FOV starts to get a bit fluffy I know but as I say, hopefully I won't be using that bit too often :D

Arthur

[Rodstar]

Arthur, I am sure your mirror is great, but if it is around the f/5 mark, I would expect that design of EP to display pretty bad coma from about 30% from the centre of the FOV. Perhaps if you just try a few across the range to see how they perform in practice. No matter how good the mirror, if the EP is not suited to a faster f ratio, if will not perform well.

[Ambermile]

OK - I see where you're coming from Rod and now suspect you may have a point. The Naglers tend to manage about 95% plus FOV before the seagulls and comets appear but I still just cannot get on with them - the "black bar" thing almost every time... and I've pretty much tried them all. My only other options appear to be the Pentax XW range. I'l have a look around and see what I can borrrow :D

Arthur

[Rodstar]

No worries, Arthur. My motto with EP's is "try before you buy".

My mirror is superb, with a Strehl ratio of 0.96 and excellent RMS, but at f/5, it shows up coma in a lot of EPs, including the Widescan, which shows particularly bad coma.

I recently borrowed a Pentax XW and a Nagler for comparison, and my opinion is that the Pentax produces better images. The Pentax design, and some of the Naglers too, have an adjustable EP design, which may help you with the image blackout problem you are describing.

At the lower end of the budgetry range, I have found the University Optics orthoscopic EP's (which retail in Australia for $125) perform very well with my fast mirror. Their only limitation is that they have a much more limited 40-45 degree FOV.

Personal preference plays an important factor too.

Good luck!

[Ambermile]

While you're here Ron - is your weather station installed inside and outside the mirror box or the house? I want something similar for the 22" and as the time for drilling holes for the ServoCAT and Argo is fast approaching I may as well do it all at once.

Arthur

PS - the 13mm should be here tomorrow so it will be interesting to see how it works out. It's a type III so should be a little better than the earlier ones.

[tak66]

PM sent!
Tak