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Meade Astronomical Telescope 291 (F=900mm f=1:14.75) on NEX
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PostPosted: Mon Nov 05, 2012 5:09 pm    Post subject: Meade Astronomical Telescope 291 (F=900mm f=1:14.75) on NEX Reply with quote
Bought that old and slow lens slow lens today locally with motorized paralactical mount, wooden tripod, Olympus OM- and T2 adapter for a few bucks Smile

I hadn't high expectation on that lens (it was already cheap 25 years ago - it did cost about 120DM with simple tripod = 90-100€ incl. inflation. And it's only based on an simple mutli-coated fraunhofer achromatic two-element lens) and bought it mainly because of it's massive wooden tripod but optical results are far better than I expected

Due it's very cloudy, raining and dark outside at the moment I made a little "spy" on one of my neighbours window Wink


(very little PP)
100% crop, added clarity and sharpened in Lightroom:

Not bad for a distance of 90 meters, 6s exposure time, shot through two windows while it's raining, huh? Smile

From what I've seen it looks much better than Samyang 650-1300mm for example and it costs even less if you can find one or a successor used.
Meade did a really good job on this lens

Now I'm waiting for clear weather and the moon Smile

Last edited by ForenSeil on Tue Feb 26, 2013 8:39 pm; edited 29 times in total


PostPosted: Mon Nov 05, 2012 5:13 pm    Post subject: Reply with quote
ah, so youre one of those nosy telescoping neighbors, huh?
kidding aside, nice results.


PostPosted: Mon Nov 05, 2012 5:35 pm    Post subject: Reply with quote
Nice find, excellent result seems way to go if need extreme focal length.


PostPosted: Mon Nov 05, 2012 6:31 pm    Post subject: Reply with quote
Excellent results!
How far is that neighbour?


PostPosted: Mon Nov 05, 2012 6:37 pm    Post subject: Reply with quote
Congratulations.

Sometimes these old-school slow achromats on motorized mounts can give great results, especially for lunar and planetary imaging (solar, too, with suitable filters). The guidescope I use (Televue TV-102) is just an f/8.6 ED doublet, and it produces very sharp images of guide stars at the center of the field. I don't know if these very slow scopes need a field flattener for best results

Slow achromats are probably not so good for imaging faint Deep Sky Objects, athough they might be OK for globular clusters.


PostPosted: Mon Nov 05, 2012 6:56 pm    Post subject: Reply with quote
Himself wrote:

How far is that neighbour?

Sorry, forgot to say that
According to google maps it's about 90 meters

s58y wrote:
Congratulations.

Sometimes these old-school slow achromats on motorized mounts can give great results, especially for lunar and planetary imaging (solar, too, with suitable filters). The guidescope I use (Televue TV-102) is just an f/8.6 ED doublet, and it produces very sharp images of guide stars at the center of the field. I don't know if these very slow scopes need a field flattener for best results

Slow achromats are probably not so good for imaging faint Deep Sky Objects, athough they might be OK for globular clusters.

Thx!
Unfortunatly I'm living in the center of an area with very high light polution and the (over-sized?) motor needs 220V (!) so I can't take it somewhere else easily. Plus the lens is so slow that a single really useful exposure of deep sky or even bright globular cluster would I guess take about 15-30min, even on comparable high ISOs - no chance without a motor!
So I'm I guess I can forget real serious deep sky with that thing, but the planets or especially the moon should be no serious problem!

I think a field flatener would be useless at the moment - my adapter sits not very tight on the telescope which produces a lot vignetting on the upper right corner Wink

PS: Your using a 3300€ ED 102/877 telescope (= 877mm F8.6 "APO" in camera language) only as a guidescope? Very Happy WhereTF is it mounted on????

Last edited by ForenSeil on Tue Feb 26, 2013 8:37 pm; edited 4 times in total


PostPosted: Mon Nov 05, 2012 11:07 pm    Post subject: Reply with quote
Good work with that.
I was thinking of using a couple of very old telescopes we have in the garage for terrestrial photography, maybe in the zoo. I have a 8"(200mm) reflector on equatorial mount and a 90mm refractor on an altazimuth mount. The 8" would be quite difficult to transport I think, and the mount is quite awkward for terrestrial photography.


PostPosted: Mon Nov 05, 2012 11:24 pm    Post subject: Reply with quote
ForenSeil wrote:

Thx!
Unfortunatly I'm living in the center of an area with very high light polution and the (over-sized?) motor needs 220V (!) so I can't take it somewhere else easily. Plus the lens is so slow that a single really useful exposure of deep sky or even bright globular cluster would I guess take about 15-30min, even on comparable high ISOs - no chance without a motor!
So I'm I guess I can forget real serious deep sky with that thing, but the planets or especially the moon should be no serious problem!

I think a field flatener would be useless at the moment - my adapter sits not very tight on the telescope which produces a lot vignetting on the upper right corner Wink


Your scope should be a good planetary imager -- f/15 to f/25 is ideal for planenary or lunar imaging, assuming the scope is diffraction limited. Also, you don't want a perfect mount and drift alignment for planetary, since you want dithering between frames of your video (that's what I've read, anyway).

If you wanted to do DSO with this setup, you'd probably need to piggyback a DSLR with camera lens somehow, and use the f/15 scope as a guidescope (if the focuser is solid, and the mount supports guiding). This way you'd shoot at f/2.8 with subexposures of a minute or two, using light pollution filters or perhaps a narrowband H-alpha filter to really cut through the light pollution.

ForenSeil wrote:

PS: Your using a 3300€ ED 102/877 telescope (= 877mm F8.6 APO in camera language) only as a guidescope? Very Happy WhereTF is it mounted on???? PS: Yes it's also two-element lens, but it's ED makes a huge quality- and price difference!


I had been using a cheap guidescope, but the focuser was not really solid, and I got differential flexure during longer subexposures with the 800mm lens. The TV-102 (no longer made) cost a lot less than 3300 Euros (maybe $2500??), but solved the flexure problem. I hope to use the TV-102 for lunar or planetary or solar someday.

This what everything is mounted on:

http://www.flickr.com/photos/s58y/4144045396/sizes/o/in/set-72157622898479554/
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