Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!

SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Collimating Meade 1000mm f11 Mirror Lens
View previous topic :: View next topic  


PostPosted: Sat Jul 03, 2021 11:52 pm    Post subject: Collimating Meade 1000mm f11 Mirror Lens Reply with quote

I bid on a Meade mirror lens on shopgoodwill.com and got it for a reasonable price, expecting it to be not so great. It's actually in great condition: glass and mirrors clean and clear, even the paint is in near perfect condition. As far as I can tell it's pretty much unused. But, image quality isn't great, and I can see points of light rendered like little Tesla logos, surrounded by rainbows. Here's a crop from a distant balloon, which was centered in the frame. (I went to a hot-air-balloon festival and they didn't fly any big hot-air balloons, but I got this one of a child's lost balloon!)


#1


I suspect this lens can be collimated and that might help. The lens doesn't have any model number or other way to identify precisely what it is, aside from the diameter and focal length on th efront. Anyone have a manual for this lens, or information on adjusting it, or advice for how to improve this problem?

Here's a couple photos of the lens itself:


#1


#2


#3


PostPosted: Sun Jul 04, 2021 10:04 am    Post subject: Reply with quote

Well there is alot on collimation cassegrain Telescopes online. I have done many but always with a star and an eyepiece. Likely it isn't out far. You have the three bolts on the back for collimation.

It it were way out and I don't think it is. You would see that by looking in the back and the reflected circles would not be concentric.


PostPosted: Mon Jul 05, 2021 4:12 am    Post subject: Reply with quote

An easy way for you to test for correct collimation when you're adjusting those bolts is to take a ball bearing -- about 1/2" (or 13mm) in diameter is good -- and glue it to a piece of cardboard, about 1 foot square or so, which is spray painted flat black. Plase the subject far enough away from the lens such that exact focus can be achieved. Shine a bright light in the direction of the ball bearing and record or observe what sort of image is produced from the point of reflection on the ball bearing. Adjust until aberrations are minimized.

Last edited by cooltouch on Mon Mar 21, 2022 11:24 pm; edited 1 time in total


PostPosted: Mon Jul 05, 2021 12:30 pm    Post subject: Reply with quote

1/2" would be 13MM or so.


PostPosted: Mon Jul 05, 2021 8:02 pm    Post subject: Reply with quote

I suspect cooltouch meant 1/2 inch (1cm) instead of 1/2 inch (1mm).

I plan to try to take the lens apart and inspect it when I get some time. I read somewhere from another person trying to collimate one that the three screws on the rear aren’t for collimating. This could be right or wrong, I don’t know. That’s why I was hoping to find a manual or some more information. The handling really is nice, it’s a shame the image quality doesn’t match.

My other 1000mm mirror lens is a Yashica and it’s really hard to use: a lot bigger and heavier, harder to turn the focus ring, and therefore I get tired even when using a monopod, and I get a lot of shakes. I really can’t use it handheld or monopod-mounted and my tripod is a lightweight travel tripod, so it’s not steady enough, and therefore I really don’t know how good the Yashica’s image quality is, because everything I’ve shot has motion blur.


PostPosted: Thu Jul 08, 2021 12:37 am    Post subject: Reply with quote

Yeah, sorry, my mistake. 1cm is what I meant. The size of the ball bearing doesn't matter that much. It should just be big enough so that it catches a reflection reasonably well.

Your Yashica may be in need of thread lube replacement.

Usually you don't find this sort of focus mechanism in something as "small" as 1000mm, but the ideal sort of focus with a large non-newtonian mirror that isn't motorised is the sort of dial knob located at the back of some larger lenses, like some Celestrion C5's, for example (5" objective size). I owned a C5 with the rear focus knob for a while and it was much easier to use than lenses with the big focusing ring one had to turn.

Incidentally, I own a Meade 1000mm exactly like the one in the above photos. I guess mine's collimation must be good because, when I can get the focus dialed in, it is amazingly sharp.


PostPosted: Sat May 14, 2022 2:09 pm    Post subject: Reply with quote

I uploaded a scan of the model 97E manual here: http://forum.mflenses.com/viewtopic,p,1563884.html


PostPosted: Wed Jul 13, 2022 11:00 am    Post subject: Reply with quote

I am searching for information online on Collimating Meade 1000mm f11 Mirror Lens and I am glad I found your post. I also found https://www.topessaywriting.org/samples/government website where I can read essay samples for free.