Conlin Hill Observatory -- 42 7' N, 71 54' W



Techniques  




What the heck is Ted up to?

2/24/04 Adventures with the ETX90: I've been trying to use the 90 piggyback on the LX200 for guiding AND for wide field imaging at F7. Click here for an explanation.

1/10/04 Star Elongation troubles I've been struggling with elongated stars in my images. Updated 1/19/04 and 2/24/04. Click here for an explanation of the issue and possible causes.

11/18/03 NEW GEAR!!! I picked up a used ST8 from Astromart. This is the same as my ST8i but it includes the guide chip. Although I may someday use a separate guide camera and scope, it will be nice having a self-guiding camera going through the main scope. I had to make up a cable to connect the ST8 to the LX200. Click here to see the cable configuration and my first light guided shot.

9/21/03 - 9/26/03 I was having some trouble with streaks of noise in my images. Click here for the explanation and cure: streaks in images.

5/30/03 The month of May has been cloudy continuously since the 3rd, 27 straight nights! On the 30th it was partly cloudy, which was as clear as it's been in a while so I took advantage and practiced guiding with the 201xt. I actually wound up with a decent M4 which I posted under the "Other" gallery. A journal of my testing procedures and results is here: Messing with the Pictor 201xt AutoGuider

3/19/03 As a requirement of the Association of Lunar and Planetary Observers Handbook, I'm trying to build up some skill in making sketches and drawings of the Lunar surface. Click here if you're interested in seeing my results so far.

1/17/03 We had 11 straight days where it snowed at least an inch each day, and plenty of clouds. But in the few times I've been out since mid-December I've made significant progress: improved polar alignment, better PEC training, and my first guided exposures which I'm pretty excited about.

I followed Bruce Johnston's fantastic new way of polar aligning goto scopes using 3 stars. His excellent write up of this technique can be found at http://members.aol.com/ccdastro/goto-tests.htm. I had very good results using this method, better tracking - stars in a high powered eyepiece stay centered all night long and my goto's are more accurate as well. Nice! If he ever gets a chance to read this, hats off to you Bruce!

I played around with PEC training for a while, training and then measuring tracking error using CCD images. PEC training is an extremely nice feature to have on a mount and I certainly recommend using the LX200 implementation of the technique. I've got some data and animations that show the POWER OF PEC.

I was having a lot of trouble with the 201XT. Basically I just couldn't get it to consistantly find and focus. I finally purchased a Ronchi focuser for the 201XT from STI. The 201XT seems to have a small critical focus point. With the new focusser I started seeing results immediately. The clouds parted and I got my first ever guided images. I should have some material on guiding in my next post.

12/8/02 At the risk of repeating myself, my 2 main problems right now are the need to obtain longer exposures, and the need to obtain better focus.


Getting longer exposures

My exposures are currently unguided and are limited to about 30 seconds (not bad at F10 with the tiny pixels on the SAC7). I've been trying to get my Pictor 201XT working so that I can take long guided exposures. My goal is to be able to take multiple 5 minute exposures which I can sum to achieve exposures in the 30-60 minute range.

Messing with the Pictor 201xt AutoGuider


Getting better focus

Here's my current focussing routine: Find a bright star near the target subject. Remove the aluminum dew shield and replace it with the 3 hole Hartmann mask. Focus the SAC7 image - the 3 "lobes" created by the mask disappear when the focus is right. Remove the Hartmann mask and put the dew shield back on. Then slew to the target, center it, and start imaging - without touching the focus.

The problem is that when the scope slews to the target, the mirror shifts ever so slightly and the focus becomes soft. I'm using a primary mirror lock/stabilizer based on the Randy Rubis / Chris Vedeler design that I purchased from
ScopeStuff, but there's still enough mirror shift to soften the focus just a tad. To get really good image detail, I've got to be able to focus AFTER centering the target. The Hartmann mask focusing method requires a fairly bright subject, plus all the scope movement associated with swapping the mask and dew shield make using it after centering the target impossible.

I'm thinking that software focusing is the way to go. This means I need software - leaning toward Maxim/DL, and a Robo-focus wouldn't be bad either. These are among the items on my
wish list.

 

Ted's thoughts on:

Imaging with the Meade electronic eyepiece

Imaging with the ETX70 and the SAC7



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