Posts Made By: Michael Connelley

Hello:
I've used one of these a lot on a 7" Meade Maksutov. The one I've used has a clear red filter that goes over the front of the scope and a tunable etalon that plugs into the focuser. I've found that it's quite touchy and finicky, and when it does work, the images don't have the contrast of a Coronado telescope. The filter bandpass is very sensitive to the tuning of the filter (a fraction of a turn of the scew will take you through the Ha line) and where the object is in the field of view. For example, a prominence that is visible at the center of the field may be invisible if the image drifts to put the same object at the edge of the field of view. While I've never done a side-by-side test, my impression is that the Coronado filters did give better images, with better contrast, were easier to use and less finicky.

Cheers
Mike Connelley

Hello:
Many metals are good reflectors/poor emitters in the thermal infrared. Gold, silver, and aluminum are the stanard metals used in coatings for IR telescopes. Today, silver is often used instead of gold since it has a lower emissivity in the IR and it still has OK blue response for optical instruments. Aluminum is also pretty good, but not quite as good as silver. More important than the metal is how clean the mirror is kept. Black objects are good thermal radiators. A telescope tube at night sees 2pi steradians of the sky, which is very cold, so the tube radiates heat like there's no tomorrow.
I don't think that white paint generally gaurantees low emissivity since paint is a rather complex chemical. Some of the telescopes on Mauna Kea are painted in a low emissivity paint, and can be white, blue, or other colors. White/unpainted tubes are useful in reflecting sunlight and keeping your scope cool if you set it up before sunset. A black scope will get hotter in the sunlight, making the cool down problem worse. My scope has an aluminum tube that I left unpainted, mostly because I'm lazy but also for the thermal issues mentioned above. By far the worst thermal problem I have isn't the tube, but the 19 lbs hunk of glass at the bottom of the tube with no ventilation.

Cheers
Mike Connelley

Hello:
You should keep the finder scope with the telrad. I find having both of them to be very useful. I'd mount it as close to the front of the scope as possible, so that it's easy to look tnrough the telrad then the eyepiece without moving around a lot. Also, the closer to the front of the tube it is, the higher up it is and thus easier to look through. You may need to add some weight to the back of the scope as I did.

Aloha from the Big Island
Mike Connelley

Hello:
The Witch Head Nebula is seen in scattered light (from Rigel), so you should go for it without a filter. Checking photos of Orion, this nebula is MUCH fainter than the Horsehead Nebula, which I usually find challenging. It also looks to be quite a bit fainter than the part of Barnard's Loop near M78, which I think I've seen once. In other words, I doubt it's visible in an amateur telescope.

Cheers
Mike Connelley

Hello:
I'm quite happy to say that someone acutally pays me to do astronomy! I'm a grad student and in 4 months I'll get my PhD. In a few minutes I'll go into work to support a visiting astronomer to our observatory, which is one of the things I get paid to do. Other than that and helping to commission a new camera, I focus on my thesis research. Quite a few of the staff at the observatories on Mauna Kea are amateur astronomers.

Cheers
Mike Connelley

Hello:
Ahh, I remember back when I was doing my first shots of the moon! Okay, it wasn't that long ago, but it was on film, using a telescope that's probably close to 100 years old. Anyway, I got some great shots without the scope even tracking. Some tips I can offer:

1) Focus carefully. You might want to tweak the focus between different exposure sequences. It's often hard to tell when you're exactly in focus, so by tweaking the focus a lot you're likely to get lucky once in a while. With the moon, I focused on the limb and craters near the terminator.
2) Take lots of pictures. Try different settings (auto, manual, etc). Keep a log of what settings were used for which exposures, so that next time you know what worked.
3) I'd try without the moon filter. That way you can use a shorter exposure time, so the drift of the moon won't be as much of an issue.
4) With the film camera, the exposure time was much less than one second. I suspect your exposure times will be a small fraction of a second.

Most of all, just experiment with it and see what works for you. Good luck!

Cheers
Mike Connelley

Hello:
C14s can certainly be good scopes for planetary observing, but I wouldn't say they're the best. They have a short tube (less wind shake), tend to have good optics as far as I've heard, large aperture and a nice long focal length with a slow f-ratio. However, the quality of planetary images probably has a much to do with the seeing and observing technique (like keeping the scope accurately collimated!) as the telescope itself since truly crummy optics seem to be rare these days. I don't see why someone with a big Meade SCT also couldn't make nice planetary images. Perhaps Celestron users are more technically astute than Meade users (I know that comment will get me into trouble!). However, one of the best webcam images of Saturn I've seen was taken with a 20" dob. The best planetary scope I've looked through is a 2.2m f/10 RC, but those are kind of hard to come by these days.

Cheers
Mike Connelley

Hello:
Your post has me wondering how something like a C11 would fare against the AP Maksutov. I suspect that the AP would win, but I have a feeling that the C11 would put up a good fight, especially considering it's about 10x less expensive. However, this is a bit of an unfair comparison since who ever paid more than $30k didn't pay so much because they thought the images in it would be 10x better than in a C11. We have a C11 that Celestron donated to the university that I work for, which Celestron cherry picked for us. I must say that it's a very good 11" scope, nice diffraction rings and everything.

More serious competition might come from a straight classical cassegrain. I guess these are near and dear to me since I have one, and I really like using it. With two fewer optical surfaces than the Maskutov (and all else being the same, also has the same central obstruction), it is capable of being as good if not better than a Maksutov. Figuring a smooth paraboloid and hyperboloid is challenging. A Dall-Kirkham will also give a Maksutov a run for its money when well made. Since the tube is open, the mirrors in a classical or Dall-Kirkham cassegrain can cool quickly. Also, if the optics are in a truss tube, the telescope is less vulnerable to wind shake. That said, the best planetary scope I've ever used is still an achromatic refractor. Ok, so it's a 16" refractor that's 125 years old, but it's still a crown-flint achromat!

Cheers
Mike Connelley

Hello:

From a certain point of view, they're both right. The central obstruction is important to get the highest constrast planetary images for diffraction limited scopes. However, for deep sky observing, the size of the central obstruction really doesn't matter since you're not interested in the details of the PSF. A 16" scope is VERY RARELY diffraction limited, which is the only time you can see the PSF structure. When the scope is seeing limited, which is most of the time, the telescope's PSF (and thus the central obstruction) are generally irrelevant. Frankly, the issue of central obstruction is over rated. Some of the best planetary images ever taken were done with HST, which has a central obstruction of about 33%. I have resolved a 0.4" binary with my classical cassegrain, which has a 32% central obstruction. In short, don't worry too much about the central obstruction.

Cheers
Mike Connelley

Hello:

I found this web page when we were taking a 7" Maksutov LX200 out of its fork. The web site is:

http://www.davidillig.com/losmandy1.shtml

I don't know how the LX50 is different, so what you need to do may be a bit different. When we took out OTA out of the fork, we didn't use the torch to loosen the locktite, but just a whole lot of brute force. We didn't have the right spanner wrench to go into the holes in disks that hold the altitude axis in place, so we tapped the holes, put bolts into them, and then used a big long screwdriver places between the bolts to turn the disk. Oh yes, we also had to remove one of the firk arms to get the tube out. To do this, we had to remove a plastic panel on the bottom of one of the fork arms to get to the bolts, which were very tight.

Cheers
Mike Connelley