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Posts Made By: Joplin Motisher-Chittenden

August 14, 2002 06:43 PM Forum: Equipment Talk

Titan mount from Orion

Posted By Joplin Motisher-Chittenden

That is a really good price for an EQ-6 but notice that the availability date is Early October which means maybe before Christmas in the case of most dealers. My guess is that they will have a huge backlog of orders and the workers in China won't be able to re-badge them as "Titan" mounts fast enough :-)

Joplin

August 15, 2002 09:20 AM Forum: Equipment Talk

Anyone ever consider a tilted Dob?

Posted By Joplin Motisher-Chittenden

There was an article in the September 1995 issue of Sky and Telescope about one made by Philip Alotis of San Francisco, CA. It was a 12.5" F 7 newtonian on a "convertible" dob mount. He used an automotive front wheel hub and brake assembly for the RA/ azimuth axis. Among the other novel features was a magnetic finder base used so that there wouldn't be any marks on the beautifully finished wood tube. I have attached a picture of it.

August 17, 2002 02:43 AM Forum: Equipment Talk

parfocalizing eyepieces, rings w/helical focusers

Posted By Joplin Motisher-Chittenden

Parafocalizing means adding spacers (metal rings or O-rings, etc.) to the barrels of your eyepieces so that they will focus at roughly the same point. It is recommended when you use a helical focuser since it can take a lot of turns (and time) to get a helical focuser to move far enough to acheive focus.

Joplin

August 19, 2002 03:53 PM Forum: Equipment Talk

90mm refractor vs. 8"SC

Posted By Joplin Motisher-Chittenden

Jake, I had an experience similar to yours a couple weeks ago. Myself and another person stayed out practically until dawn at a star party and one of the last things we checked out was Saturn. He had a nice 10" LX-200 which had been providing very sharp views all night long. I had my Vixen FL80S (an 80mm fluorite refractor). The conditions were admittedly pretty crumby seeing wise, saturn was even inconsistent in the refractor. The views were quite similar in each scope aside from the much brighter and more colorful image in the LX-200. The image was more consistent in the refractor of course, due to the variable seeing. I was using a Siebert 7mm and a 3 element 2x Barlow (very nice combo for about 180x) and he was using Meade plossls. At first the image in the LX-200 was really a mess since the power was almost 300x? but then he dropped the power down to about the same that I was using.
I think the following factors had an influence on the comparison:
1. Seeing, which was admittedly bad
2. Collimation of the LX-200 which hadn't been thoroughly checked
3. There was a rapid temperature drop which may have exceeded the LX-200's ability to cool down.

My question for Jake would be how are you checking the collimation on your LX-200 ? From what I have seen it is extremely critical on objects like Jupiter and Saturn.

Joplin

August 24, 2002 12:44 AM Forum: Equipment Talk

Re: 2" Diagonal Preferences and Opinions! SC

Posted By Joplin Motisher-Chittenden

Close, with a Televue 55mm Plossl you can get an actual field of 0.94 degree :-)

Clear Skies,

Joplin

August 29, 2002 05:35 AM Forum: Equipment Talk

Vintage Newtonians

Posted By Joplin Motisher-Chittenden

Walter, don't forget Parks, they have been known to make some really good mirrors and their lightweight fiberglass tubes are great. I just purchased a Parks 10" F6 that had been languishing here on Astromart for quite some time, waiting for a local buyer (thanks, Tom!). It is sort of a diamond in the rough as the optics are great but the mount has been heavily used. I've had it out a couple times (not exactly a grab and go scope compared to my 5lb refractor :-) under fairly crumby conditions but it is still obvious that the optics are first rate. It is around 20 years old. One thing I have discovered is that this is positively the largest equatorial telescope I can transport and that it pretty much consumes the interior of a Plymouth Horizon (no passenger space). I'm not sure how much the 1.5" shaft/ 10" gear equatorial head assembly weighs (50 lbs+ ?) but I do know that it helps a LOT to remove the declination shaft. I plan to put the scope on a Dob mount and set the Equatorial up in a permanent observatory eventually. One other note: this scope came with a G-11 saddle plate and a dovetail for the scope - it is indespensible and makes attaching the OTA to the mount a million times easier. I realize that Parks equipment is really expensive new - but you can find some amazing deals on these big Newtonian here on Astromart. By the way, how is that Coolpix 4500 working out for you ? I've yet to purchase a digital camera but that may be the one I end up getting.

Joplin

September 1, 2002 12:54 AM Forum: Off Topic Discussions

These Guys "Bug Me ! " How about you ?

Posted By Joplin Motisher-Chittenden

It is sad, but sometimes the rest of us can get great telescopes at good prices from these people. That was how I got my Criterion RV-6 (6" newtonian on an equatorial mount) a few years back for about 25% of what they go for these days. I had a couple junk scopes when I was younger but happened upon this gem in the local classifieds. The owner used it a bit but was getting older and grew tired of setting it up. It helped renew my interest in astronomy.
I was working at a photo lab a while back and noticed another RV-6 in some photos of a flooded basement. I thought about trying to rescue it from such a horrible life but it looked like a lost cause as the tube had a water mark on it about a foot high. It made me sad though to see such a fine instrument wasting away like that.
This also brings up the point that the best telescope to have is the one that you will get the most use out of. I have a 80mm fluorite refractor that now sees much more use than the RV-6, even more so since I now live in an apartment. I have to travel a fair distance to get to dark skies and the seeing usually stinks here anyway, so the refractor is a much better all around telescope for me. Of course, I just bought 10" newtonian on an equatorial mount - mild case of aperture fever. I am going to build a dob mount for use when the equatorial is unnecessary. I promise not to become one of those people that has telescopes as furniture though :-)

Clear Skies,

Joplin

September 3, 2002 09:38 PM Forum: Telescope Making

Modifications to Dovetail Finder Brackets

Posted By Joplin Motisher-Chittenden

Barry,

Could you measure the inside diameter of your Orion 50mm bracket, I'd like to make sure that the 50mm finder I have would fit in it (53mm outside diameter).
It is a great old Parks finder but I desperately need a dovetail bracket for it since it keeps getting knocked out of alignment when I move the scope.

Thanks,

Joplin

September 11, 2002 07:48 PM Forum: Equipment Talk

ST80 Telephoto lense for Canon EOS (problem..)

Posted By Joplin Motisher-Chittenden

You will need additional extension in order to get the eyepiece projection setup to work. The field stop of the eyepiece will need to be at the same point that the camera's film plane would be normally. You will probably need at least three additional inches of extension. There are several ways to accomplish this: 11/4 " diameter extension tube, T-thread extension tubes, or EOS mount extension tubes. Also, you will probably find that the effective focal length yielded by the eyepiece projection combination will be at least 1000 mm, probably more. You will need very fast film, a solid tripod, and cooperative wildlife subjects in order to get good results with such a setup. You may be happier in the long run getting a 500 mm or so t-mount Telephoto lens at a Camera Show (they can be had for $50 - $75 if you look around). The optics will be better for photography, it would be easier to focus, and the camera mounting is much more secure (would still need extension tubes for close focus work, though).

Joplin

September 12, 2002 07:57 AM Forum: Equipment Talk

Orion Apex 90 for Wildlife

Posted By Joplin Motisher-Chittenden

Trey,

I have used a Meade maksutov spotting scope for wildlife photography with so- so results. I must admit that the optics in the one I had were not that good. The main problem with using it was the dim viewfinder image as it was a 90 mm F 11 (1000 mm f.l.) scope (accounting for light loss and the central obstruction it was more like the equivalent of an F14 lens). The Apex 90 has an even longer focal length (1250 mm f.l.) at F 13.9 so the actual transmission will be over an F 16 equivalent lens. The bottom line is that, even with a bright focusing screen, the image is going to be too dim to focus well. Astrophotographers are always looking for the fastest setup (lowest F-ratio) so they can use shorter exposures. The same is usually true of wildlife photographers. The practical limit for wildlife photography is F8 or so, and F5.6 is a lot better. Once you get past that, you get diminishing returns as the image will be larger but the overall quality will be lower for a variety of reasons.
If you must have more focal length than 400mm a 1.4x teleconverter would work well (and it won't change the focus point of the camera) as it would give you 560 mm at F 7. A 2x teleconverter would give you 800 mm at
F10 but then you will run into focusing issues and image quality issues.

Hope this helps,

Joplin