Sunday, February 07, 2010

Testing Guiding with the CGEM

Twas a clear night, last night! I headed out to the local observing spot and was actually surprised to see that nobody else was out there. I guess everyone I knew sought after darker skies. I was ultimately joined by a good friend and his wife for a while. He was taking wide fields with his Nikon D90.

My interests last night were in setting up autoguiding for the CGEM. I would do this with my Meade DSI and William Optics 66mm refractor. My laptop battery was rather limited, so I didn't have much time to do it. I was using the PHD-Guiding freeware guiding program. (By this time I had also setup the mount with two-star alignment, three calibration starts and a precise polar alignment.

My first task was to get the image from the DSI. I had to tamper with the settings a fair bit, as previous attempts saw a massive amount of horizontal banding in the image, much like an out-of-tune TV signal. I figured that this was the result of too high a gain setting, and when I lowered that, as well as increased the exposure time on the camera, I was able to get a decent star image.

I then connected the cable from my laptop to the CGEM. The issue here was that the software had multiple mount types listed in its mount selection menu, but nothing really suggested to anything related to Celestron. I took a chance and selected the "Generic Hub" option, which I think relied on the ASCOM drivers already installed. I selected a star on the screen to guide with, and the program very quickly indicated "Guiding" at the bottom of its window. SO, I shot a snap of M42 for five minutes for a test. The resulting image was fine, but there was star movement when I zoomed in really close to examine the image more properly. I am thinking that I didn't have the right mount setting...

Sadly, at that time my laptop battery died! I really need to buy an inverter for when I am out in the field. My power supply should be ample to handle both my mount and a laptop for many hours between charges.

I spent the rest of the night messing around taking different snaps of clusters, just for fun. But my power supply ran out at about 11:30 and I had to head home as a result. I'll work on the guiding and get all of my factual ducks in a row, and then hopefully next week I'll try my first guided image from a dark sky spot...


Jared said...

Ya, it sounds like you didn't have the mount selected correctly. You need to select ASCOM from the mount menu and when you click the telescope to connect it will prompt you for the mount type. You'll have to install ASCOM for this to work...I would try and get it connected prior to heading out next time.

I'm planning on going out mid week to get some H-Alpha. If you'd like to join me let me know. We can probably hook your laptop up to my power pack as well.

Nice M45 Image BTW!

Phil said...

Hey Jared!
Yeah, so I selected the ASCOM option but was told I didn't have everything for that. You're right, I should have tested comms with the mount at home prior to going out. Next time...
Will keep an eye on the WX this week. I am booked each night until Thursday, so will touch base with you.

Tim Long said...

Can I recommend the new ASCOM Answers Q&A site? You'll find some of the Gemini driver developers there, so you should get a good quality, authoritative answer.

--Tim Long

Phil said...

Hi Tim,

Turns out the issue was with my Serial-to-USB cable. I tried a different connector and it worked out just fine.

Thanks for visiting, though. I'll visit that site for sure.


tim™ said...

Hi Phil,

I'm new to PHD guiding, I recently purchased the KWIQ Guider (QHY5 cam + scope), it's great guider/setup.

I also own the CGEM mount, I use a C8" SCT or my Vixen ED80sf. Wondered if you had any specific settings in PHD for the CGEM mount?

Thanks & Clear skies,

Phil said...

G'day Tim - thanks for dropping by!

Using PHD with the CGEM was really easy. I just made things difficult by plugging my guiding cable into the guiding/RS232 port on the mount instead of on my hand controller! One night wasted because I didn't RTFM!

Once I had that sorted, it was VERY easy. I had to download the ASCOM driver system with Celestron-specific drivers, and just point the PHD software to the scope via that drivers' software (pretty intuitive). I only had to make adjustments to the view for my guider (I use an older Meade DSI)which was producing a lot of noise (just turned down the gain value). Other than that, I did not change anything else in the PHD software settings and can guide easily for 5+ minutes!

One thing to note. I always use the "Auto Select Guide Star" option to let the software determine the best guide star. Sometimes the crosshairs will appear to land on an empty space, but trust the software - it has located and locked onto a guide star.

Good luck and let me know how it goes!


Anonymous said...

Hi Phil,

Very frustrated here. I have the QHY5 running with PHD but can't get it to speak to the CGEM. I've run the 6 pin cable from the st-4 port on the camera into the CGEM 6 pin autoguiding port. In your above note you suggest that it should go into the hand controller ... but it's only 4 pin.

Lil help?



Phil said...

Hi Herb,

I am in fact using a four pin phone line connector for my PC to CGEM hand Controller connection...