Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Topics - Dale Khan

Pages: [1]
There are several premium dob makers, several astrophotography vendors, more eyepiece brands and series than you can count (with several premium options, not just one or two), many premium scope brands, all kinds of different optical designs to choose from etc.

I guess we should consider ourselves lucky that we have so many choices and that the industry is so competitive

I have read a LOT about the Explore Scientific 82 degree line. I have the 8.8 and the 6.7 and like them very much.

I wanted something around 5 or 5.5 for my XT8i as my 4.5/266X Meade HD60 gets very little use. I typically don't have conditions to support that high magnification. So I wanted something closer to 220X but ES doesn't offer an 82 at 5.5. As my XT8i is manual tracking I prefer the wider AFOV in the higher magnifications. Above 10mm I typically use a Celestron or Baader Hyperion Zoom. And my GoTo scopes track so they really don't need the wide AFOV.I was at NEAF and saw the Meade Series 5000 ultra wide angle 5.5. Did a quick look up and it seemed to get very good reviews so I purchase it at a show price 10% discount with tax included. Not a bad deal.

Got it home and had 2 opportunities to use this on Jupiter. I like it a lot. Seems every bit as good as the ES 82s.I am not sufficiently experienced or knowledgeable about eyepieces to provide a detailed review other than to say I am happy with my purchase. But I would like to see what other people think about the Meade line, especially compared to the ES 82.

The Meade are a bit lower in cost at regular price. $129 vs $149 typically. Theyseem like a better value to me. But I don't see them mentioned very often.What is your opinion?And what of the Celestron Luminos 82 degree? They are typically around $100, which islower than ES or Mead. Do they compare well to these two? Could they all be the same glass under a different label? They are all 7 element designs.Inquiring minds and a straining wallet want to know.

This thread shows a 2-mirror null corrector solution I got tonight to test a 1 meter hyperboloidal RC primary mirror in double-pass auto-collimation (DPAC).  The hyperboloid is 1000mm aperture, vertex radius 3950 mm, CC = -1.033.  The hyperboloid will be tested in DPAC with a large and very well-made optically flat mirror having an 8 inch central perforation.  The DPAC focal point has several waves of spherical aberration that must be removed with a null system.  The 2-mirror null mirrors are both spherical, one being concave and one being convex.  OSLO file and prescription attached.  The DPAC system residual aberration is around 1/20 wave P-V, which meets the test requirements.  I have done 2-mirror reflective null correctors before where both null mirrors were concave, similar to the one used for the Hubble primary (with the unfortunate spacing error), but this is the first nuller I've developed that has both concave and convex spherical mirrors.
I used ZOS 16.5 to design it, and keyed it into OSLO-EDU for wider use on CN's ATM forum.  Notice that I didn't include special apertures with holes through the test flat and null mirrors.  I think I found a program bug in OSLO-EDU in that I could not get the system to raytrace and analyze properly if I included the central holes.  Anyone else experience this bug? 

Eyepieces Questions & Recommendations / 20mm eye piece question
« on: December 26, 2017, 07:04:05 PM »
Ok , Ive been needing the 20mm Nagler type 2 20mm for a very long while, and while accessible used, theyre still very quite costly, relatively speaking for some one on a fixed disability income. inquiry is exactly what ep can be found , likely used, that is a close equal to the 20mm type 2, in a 2 inch format ?

Size and weight are desirable , to help balance the C6R, lol

Beginners Forum / 2 inch eyepiece education needed
« on: December 25, 2017, 09:06:17 AM »
Hello all!  I've been lurking round the past couple weeks trying to learn.  Purchased a Skywatcher 8" Dobsonian 1200 mm recently.  After literally 60-plus hours reading what I could to grasp the basics (I don't know if my eyes will work to check through the telescope) I have the energy to search for answers-so I will just ask, as you appear to be a wonderful group.
I had been only looking for some clarification on 2" eyepieces with the broad and ultra-wide AFOV at greater forces.  Apart from money, is there any disadvantage to these?  I had been thinking about picking up Owl Astronomy's15 millimeter Ultra-Wide Angle - 2 inch.  Is there any advantage to 1.25" eyepieces?  Many thanks

Reflectors Telescopes Forum / Just purchased Used 18 f4.2 Starmaster
« on: December 24, 2017, 05:33:57 PM »

My dob search is OVER!  Simply put down my deposit 18 Starmaster f4.2 with GOTO.  I am THRILLED!!!!


I will be picking it up the week of October 11th.  At least, now I can relax, stop searching, and start viewing!

All the best to you!!!!!


Beginners Forum / 80mm finder scope
« on: December 24, 2017, 02:38:09 AM »
It was suggested that I replace the 5x24 finder scope for valid reasons when my new employed 114EQ-D shows up, and it s on its way.  I'm getting anxious to give it a once over before I take it out for the first time.

I started searching on the internet to get a finder and believed about usinga small 80mm celestron I'd picked up, made it used back in the 1990's when I was active in benchrest, used it to get a target spotting scope.

I dug it out yesterday, would there be a more sensible way to mount this to the Newtonian telescope?  I looked at scope rings this morning but I really don't believe that they will fit because of the mount on the base of the celestron, any ideas?  See attached picture, it mounts to a camera tripod.

Thank you,

Attached Thumbnails

Pages: [1]