Posts Made By: Gene Griggs

I've got a new Meade DSI on order (finally shipped). After waiting almost 2 months.

In the meantime I've seen some tremendous astrophotography photos from the Canon 20D posted on this website.

From some of you experts out there -- what's going to perform better for astrophotography using a 7" Mak and 4" Fluorite refractor on the usual astrophotography suspects, a Canon 20D or Meade DSI?

Also what is the size of the picts I see of the 20D's? Are these capable of producing 5mp & 8mp pictures of astrophotography versus the new Meade DSI of perhaps 1mp....

Perhaps the Meade DSI will beat the Canon 20D significantly on sensitivity or maybe not? Does anyone know the answer to these questions....

I'm trying to figure out if I'm better off just spending the $1500 and getting a Canon 20D and selling my new and not yet received $300 Meade DSI --- or go with a cheaper camera like the Canon 300D rebel (which is also capable of astrophotography to some extent) and keeping the Meade DSI. Any experienced input is greatly appreciated.

Here's my first images using a Canon 20D with a Vixen 100mm Fluorite (no focal reducer used). Both of these photos posted are short 15-30 second unguided photos using ISO 800 or ISO 1600 at prime focus.

I've seen one software product (about $45) on the market that helps focus the Canon 300D, 10D and maybe with a bug or two the new 20D then there's the $200 manual setups. Does anyone have any recommendations on what system works the best considering I have a laptop I can use to connect to the Canon 20D if required.

First image is a shameless plug -- Seven Sisters.

I'm a little puzzled and need some help from one of you pro's out there using a Webcam as an autoguider. I have a Philips Toucam on one of those Chinese clone 80mm short tube refractors(400mm focal length) which is going to be used strictly for autoguiding.

I bought this Toucam new in the box and then purchased a Moog screw on adapter (there's no lens on this webcam anymore just the ccd chip).

My question is when I connect my Toucam to this short tube and focus it - it has a very small field of view and appears I'm at a very high magnification like 100X and at the upper end of the magnification of what this scope will take and using it at prime focus (no eyepieces). This very small field of view makes it difficult to find stars / focus and use them for autoguiding. I've spent 20+ minutes just trying to find a star with this thing before giving up. Am I doing something wrong or just not patient enough?

I've seen focal reducers for use on a webcam but didn't think it would be critical when using a short focal length refractor. Am I wrong or missing something here?

I'm picking up an old Maksutov Cassegrain ATM project that was never quite finished. Scope was partially made probably back in the 70's or early 80's. Mirrors are out getting recoated and there were a few parts missing on this old OTA.

1. I need to locate a mirror cell for an 11" mirror (yes this is a big mak!) that will fit the 12.7" diameter tube.
2. Large metal back on back of OTA for attaching a focuser is about 2 3/4" and is threaded. Any ideas where I could send this part and get someone to attach a focuser?
3. Know anyone who can MgF2 coat an 11" Meniscus that doesn't cost a mint?
4. Where can I get a filtered cooling fan / power supply?

The joys of a scope project! I wouldn't do this but it's a once in a lifetime type project that I will never repeat.

Clear skies and thanks for the help!

I have a large ATM Maksutov Cassegrain project that's around f/6.5. Before I finish this out I'm curious if it's possible to use the same corrector and primary but just switch the secondary and make it a Mak Newt...

Has anyone ever tried this on a slow Mak Cass design -- or is it simply not going to work due to the correction of the meniscus? Note: The secondary is not a spot on the meniscus but an actual secondary mirror with no magnification.

Has anyone figured out a way to use 1.25" or 2" filters with a standard SLR T-adapter. The T-adapters all seem to have 2 sets of threads but they're slightly too big and slightly too small for a standard 2" filter. Plus they're too big to use a 1.25" filter.

So you can't use a filter with a SLR when connecting directly to a refractor for prime focus shots which doesn't make sense... There has got to be a step ring or combination of step rings (or something) that would make using 1.25" filter screw into a T-adapter. Has anyone out there figured this one out?

Has anyone figured out a way to use 1.25" or 2" filters with a standard SLR T-adapter. The T-adapters have 2 sets of threads but they're slightly too big and slightly too small for a standard 2" filter. Plus they're too big to use with a 1.25" filter.

So you can't use a filter with a SLR when connecting directly to a refractor for prime focus shots which doesn't make sense... There has got to be a step ring or combination of step rings (or something) that would make using 1.25" filter screw into a T-adapter. Has anyone out there figured this one out?

I use a have my Meade 7" Maksutov on the LX200 Classic mount which supplied power to the cooling fan on the back of this Mak. I sold the mount and now need to figure out how to power the fan. It uses a standard connection and I connected a 8 AA batter power pack to it just to see if it'd work. It seemed to work fine but appeared to provide move power than required so I disconnected it after only a second or two as I didn't want to burn up the motor. Does anyone know the specs or power requirements on this motor?

Thanks!!!

I'm wanting to build or buy a small Newtonian OTA for astrophotography. I'm assuming this is the place to ask. I've seen several companies such as Tak and Orion Newt OTA's for astrophoto. The Tak is 180mm F2.9 (7") and priced at $4200. The Orion is a skimpy 4.25" F4.0 but very cheap at $139.

This is where I need the help. I know there are numerous places to purchase quality mirrors varying from 6" to 20" in a variety of focal lengths.

What I'm trying to figure out is:
1. Should I stick with a 4.5" near F4.0 or will a 8" F6 give even better images (considering both primaries have similar Strehl ratings). Or would a 6" F6.0 be a better choice? I realize the 8" collects more light which means less time on exposure time but I'm ultimately interested in flat field and the quality of the photo.

2. Where can you get a short focal length mirror like the Tak?

3. Am I better off just buying a finished Meade SN6 or SN8 or a small Mak Newt that have decent optics versus going for a high end custom reflector with a 0.98 or better strehl?

I already have a nice motorized focuser and would like to keep the OTA under $400 - $600 if possible.

I'd like to thank everyone on this forum for helping me out with some initial questions. I have now found a really nice 8" f4.92 mirror.

I'm putting this into a Konus tube that originally housed a 8" f5.0 mirror. My goal is to optimize this for astrophotography but still want to use it for visual.

Are there any recommendations regarding mirror spacing or should I just use the original spacing Konus had for both the primary and secondary and plan to use a focal extender for astrophotography? Or are there some tricks such as moving the primary 1" closer to the secondary or somethng?