Survey - Messier Objects in 4-1/4" F4 Newtonian Telescope on Meade LXD75 Mount


This is the first program for the observatory and was started in October of 2011. It's primary goal is to test the autonomous operation of the observatory and it's associated equipment to identify and correct any shortcomings. A secondary goal is to create an image catalog of all Messier objects visible from the observatory with it's 4-1/4" F4 Newtonian telescope and modified Meade DSI II Pro camera. I want operations with the smaller telescope to be routine before switching to the 10" F4 Newtonian.


The first problem I encountered was with collimation of the optics. A cheshire collimator was used to get things close by the usual methods (as in this document) and then the camera was inserted and set to be slightly out of focus. At this point, the primary mirror's collimation screws are used to bring the out of focus star images into symmetry about the center of the field of view. You can see an improvement due to collimation in the images below:

Polar alignment

I spent about half a night getting the mount polar aligned. I used the drift alignment method and the drift explorer in k3ccdtools. After several hours of iteration I got to within about 10 arc-minutes of the pole. I also shimed the OTA so that the optical axis is more parallel with the RA axis of the mount.


Another problem was with maintaining focus. My telescopes have very little temperature related shift in focus and I was hoping that an motorized focuser wouldn't be needed (at least not right away). But due to a combination of factors (filters in the light-path, mechanical movement, residual temperature related movement) I do end up needing to tweek the focus every now and then. Hence the addition of computer controlled motors to my two JMI focusers, more information is here.

Goto Accuracy

After fighting to find objects (in the smallish CCD field of view [FOV]) I realized that something would need to be done about the limitations of my Meade LXD75 mounts goto accuracy. So, I setup a virtual machine (running Linux/CentOS) and installed software. This software accepts images of star fields and returns the location (RA, and Dec.) Then, I integrated with my Sky Planetarium software and this allows me to quickly locate objects.


This involves attaching an small refractor with it's own CCD camera to the side of the main telescope. This smaller telescope/camera provides images every few seconds to allow corrections to the motion of the (LXD75) mount so it tracks more accurately during long exposures with the main telescope. Without autoguiding I was limited (by star trailing) to 40 second exposures or so, with it, exposures can be of any practically any length. This opens up a range of targets that are simply unavailable at shorter exposures. The following raw unprocessed images illustrate the difference (40 seconds vs. 8 minutes).

Software - Sky Planetarium

I use my own custom software to control the telescope and cameras. I needed to add some features to aid in getting more productivity out of my setup.

Camera sharing: Sky Planetarium supports the Meade DSI family of cameras (and most web-cams too). I added camera sharing support as the plate solving and imaging console must both use the same camera.

Telescope control: Now can use refracted coordinates for ASCOM supported telescope mount gotos to help with the initial pointing accuracy.

Plate solving: Sky Planetarium aquires images and passes them off to be plate-solved (by the software). It then picks up the resulting coordinates and shows where the location is in relation to the stars/objects on it's map. In automatic mode, after a user requested goto completes it takes an image and waits for a successful plate solve, then moves the mount to the corrected location. The mount can be moved via another goto, a sync-and-goto, or a slew (Autostar only). This is all implemented but more debugging and testing is necessary. Still, this works well, getting the object easily within the CCD's field of view (+-1/4° from center) every time. More work needs to be done with the slew support and mount tuning to improve upon this. I want about 4-8X this level of accuracy.

Imaging, automation: I've added the ability to pre-configure the filter/exposure-time/number-of-images and have it shoot all of the frames for color with a single button press. The way it's setup now, there can be only have one exposure length, I'll eventually add the ability to specify the exposure length/number of frames for each filter.


3-14-12, Messier Survey:
I added a few more objects to my collection. Below is an new image of M1, the Crab Nebula. I also imaged three more open clusters. Two of these clusters have a companion object and are quite interesting. Just visit the gallery to see the latest images. I believe that I'm getting the best results possible with this telescope/camera combination. I'll need to make some improvements to my modified Meade DSI-II Pro (especially it's filter wheel) and to the little 'scope to improve on these results substantially. So I'm switching to the large 'scope and DSLR combination next chance I get.

1-26-12, Image Gallery:
I did some work to improve the Image Gallery on this site. If I'm going to image all of the Messier objects, they should be readily available for display...
First, the sorting of the list of recent images was updated to use the date the image was taken (from a resource file) instead of the file write time (that was messing the order of things up.)
Then, I added two new categories to the Image Gallery. One for listing out all of the objects by Messier number and one by NGC number. These lists of objects are sorted by name with additional (older) images of the same object added in "+" links after the name to keep the list compact and readable.

1-21-12, Messier 33, again:
Nice clear moonless night. I still wasn't satisfied with my image of M33 so I added a 50mm Guidescope and second camera to enable autoguiding and went up to longer exposures. The sub-frames used for this image were 8 minutes each. Even with this long of an exposure time, -20°C cooling of the CCD is sufficient. The hot-pixels are noticably more numerous but managable without using dark frames. I might have to see what happens and take the CCD down to -30°C, but it just wastes time when it ices up and I have to mess around with warming it back up to get it clear so I didn't try. Nearly 3 hours of exposure were used to make this image, it consists of 5 each of L,R,G,B (8 minute subs).

1-15-12, Messier 1, 42, 43, and 78:
Another clear night. The Moon had yet to rise so I had nice dark skies, still my session was cut short by clouds rolling in around 10pm. The M42/M43 image is composed of 30 second frames, twenty each of L & G. R had seven frames and B only one as it got cloudy right in the middle of my imaging session. The M1 and M78 images were made from 30 second raw frames, ten each of LRGB.