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Posts Made By: Joplin Motisher-Chittenden

September 16, 2002 09:49 AM Forum: Equipment Talk

focal lengths and light pollution

Posted By Joplin Motisher-Chittenden

At the same magnification two 8 inch scopes of different focal ratios will have the same contrast. However, on a newtonian (dob) if you increase the focal ratio, you can use a smaller secondary mirror, which will increase contrast a little bit. The effect is lost though if you switch to a sct from a dob since the sct design requires a larger secondary mirror and more optical surfaces (which scatter light, reducing contrast). Assuming good and clean optics on both, the newtonian will win on contrast. A good 6" refractor will appear to have better contrast than either of the 8" reflectors on bright objects at the same magnification becuase the refractor gathers less light and scatters less light which will definitely darken the sky background.

Joplin

September 21, 2002 08:38 PM Forum: Telescope Making

Slipping Crayford

Posted By Joplin Motisher-Chittenden

I would call Apogee and ask them about it, they still sell it and I'm sure they would be familiar with it's adjustment quirks.

Joplin

September 22, 2002 12:01 PM Forum: Equipment Talk

Hello everyone newperson here,got some questions

Posted By Joplin Motisher-Chittenden

Darren,

I've put together a short list of what would probably be the best scopes within your budget. Since space is a constraint for you, longer newtonian reflectors probably won't be a viable option. Newtonians with F-ratios like F5 make for more compact scopes and are fairly popular right now. The main thing to keep in mind is that these fast newtonians are somewhat frustrating to collimate for the beginner and will require periodic touch-up to get full performance. The other options are refractors and maksutov-cassegrains. A good refractor is an excellent first instrument since it doesn't require much maintenance to get full performance out of it. Refractors with faster F-ratios are more compact and easier to transport but they will suffer in optical quality. A refractor with an F-ratio of F10 will have a lot less chromatic aberation than an F5 one and also lets you acheive higher power without a barlow (which can add more color and degrade the image unless you spend the money for a good one). A maksutov - cassegrain is a good choice if you need the most compact instrument available but is limited to high power use as the focal ratio is usually quite long (F 12 or more, usually). My first choice would be a refractor of 4 inches or greater aperture with a focal ratio of about F10. The Celestron C102 HD is an excellent value at about $400 new. The Russian Tal 100R has the same size optics and focal length at about the same price. It is heavier built and probably has slightly better optics. The Orion StarMax 127 would be my choice for a Maksutov. The Meade ETX series has more consistent optics but is more expensive. For a newtonian I would go with the Orion SkyView Pro 6 EQ (definitely would go for the optional polar alignment scope or a similar scope.) For photography, dual axis drives will be indespensible. If I had to narrow the choices down to one scope it would be the C102HD since it would perform very well on objects that beginners usually like to check out like the moon and planets and would be available with dual axis drives for about $550 new. Unfortunately, most of the equatorial mounts in this price bracket leave a bit to be desired, the only way to get around it is to spend more money.

Joplin

September 22, 2002 11:11 PM Forum: Film Astrophotography - Imaging and Processing

no batteries camara

Posted By Joplin Motisher-Chittenden

The only one of the big four Camera manufacturers (Canon, Minolta, Nikon, Pentax) that still sells a fully mechanical SLR is Nikon (the FM10, FM2, FM3A). The FM10 has a Nikon bayonet mount but is built by Cosina in Japan and has an all polycarbonate body, match diode meter, and mechanical shutter that doesn't require batteries. The polycarbonate body is plenty sturdy, though I have seen them crack when an older metal camera would just get dented. The FM2 is an older design that is still produced, and is one of the classic Nikons ever made but is somewhat expensive. The FM3A is a hybrid manual and electronic camera, also expensive. If you want interchangeable viewfinders, the recently discontinued F3 is the best option but is also expensive.
Pentax recently discontinued their venerable K1000 but there are a couple low cost alternatives that use the ubiquitous K-mount. The Vivitar V3000 has similar specifications to the FM10 and is also made by Cosina in Japan ( It is also cheaper, the camera and 50mm lens can be had for well under $200 new ). The Kalimar K90 is the Chinese entry, similar specifications (not sure about the quality). By far the best deal I spotted was on Ebay - Ritz camera is selling Ricoh KR-5sv cameras with the lens and body only dirt cheap. One of the bodies sold for just $61 a while back. The KR-5 series was Ricoh's most popular manual camera until they stopped making them a couple years ago. They have a good reputation - I even know of one professional photographer who used them all the time!

Joplin

September 27, 2002 02:15 PM Forum: Equipment Talk

A question to Experts

Posted By Joplin Motisher-Chittenden

That lens is designed as a complete optical system, removing any of the elements will cause a huge decrease in performance. If you need a telescope that is well suited for photography and viewing, I would consider the Borg 100 mm ED. Depending on the condition of your lens, you could sell it and easily afford a used Borg optical tube assembly.

Joplin

September 29, 2002 09:15 PM Forum: Deep Sky Observing

Just saw Uranus & Neptune!! -- 1st time!

Posted By Joplin Motisher-Chittenden

Miguel,

I observed Uranus, Neptune, and Pluto a few weeks ago with my 10" newtonian. Uranus had a similar appearance to what you described, a small greenish disc. Neptune had a smaller disk with no discernable color. Pluto appeared pretty much starlike but was worth finding just for the fun of it. The weather here has been really bad but I did spot the Nova in Sagittarius last night through binoculars, it was about magnitude 7 or 7.5. When the weather clears up I'm going to seek out the Asteroids Ceres and Melpomene in the Constellation Cetus. Both of them are about the same brightness as the nova.

Clear Skies,

Joplin

October 1, 2002 11:25 AM Forum: CCD Imaging and Processing/Solar System

Green lighs and Astrophotography

Posted By Joplin Motisher-Chittenden

If there is any moisture in the air at all I find them very annoying and there is no doubt that the beam could appear in astrophotos, particularly when using a fast widefield setup. I would recommend restricting the use of them to twilight or not at all since they are hardous anyway. At a staryparty there is a liability issue since they can damage vision permanently if used incorrectly.

Joplin

October 14, 2002 02:33 PM Forum: Takahashi

Re: diagonal focus

Posted By Joplin Motisher-Chittenden

David,

This recessed adapter would probably do the trick (bottom of the page on this link):

http://www.astrosystems.biz/focm1.htm

Of course, you might run into the problem of eyepieces and barlows with long tubes hitting the diagonal mirror.

Joplin

October 15, 2002 12:23 AM Forum: Meade

Meade LXD55 SN-10"

Posted By Joplin Motisher-Chittenden

Matthew,

It has 1/4x20 tapped mounting points the top of each tube ring. The best way to utilize them would probably be to put a piece of aluminum between the two points and drill an appropriate size hole for a small tripod head in the center. It could double as a handle for the scope during transport. All that would be required would be drilling two 1/4 holes in the aluminum at the proper spacing and one in the center (either 1/4" or 3/8", depending on the tripod head), then attaching the head with an appropriate length screw when it is needed. This has the advantage of being much secure than using just one of the mounting points and will greatly reduce the chance of flexure.

Joplin

October 21, 2002 04:47 PM Forum: Equipment Talk

Park Reflector

Posted By Joplin Motisher-Chittenden

Ted,

I've got a 10" Newtonian that was made by Parks in California back in the early 1980's. The optical quality is great on mine; Parks was and is still known for producing high quality optics and fiberglass tubes.
What size is the newtonian you have? (Parks has made quite a few and also imports some scopes).
Here is the link to the current Parks website:
http://www.parksoptical.com/

Joplin