Log - Comet Holmes 27 Oct 2007
Hi All,
On 27th night we planned observation and photography of Comet 17/P Holmes. I went to Nilesh's place at Pune as Nilesh has almost Observatory Setup !!!
We means Myself, Nilesh Desai, Sagar Godambe and Abhir Joshi. We met on dinner late night and then reached Nilesh's home at around 11:30 PM. Then we started setting up his 12" Mead SCT telescope on Losmandy G-11 mount. It was more than 100 Kgs of equipment to be transferred to terrace!!! The whole set up took around one hour and telescope was ready for visual use... Unfortunately we did not have finder scope for 12" and can not set small refractor on 12" as a finder, as it did not leave any space on mount after putting 12 Tube...
The First look through 12" :
Using TeleView 40mm Plossle on 12" ( F = 3950mm) it provided us 99X magnification, We stared "searching" for comet which is very bright our estimate was 2.4 mag. It was really easy to find even without finder. we centered it and G-11 mount tracked it for rest of the time of observation peacefully...
Then we switched to high power... Using 15mm TeleView Nagler it was almost 264X, The comet was almost 1/3rd of visible field :o. HUGE !!!! a very big, bright and detailed version of what I have seen in one 4" before.
The comet was distinctly bigger and very bright with star like nucleus and around 4' arcminutes Coma which is off-centered in side big Halo of about 8' arcminutes. The starlike nucleus was on the southern edge of off-center coma. Coma was little oval in shape. The coma was on Northern side of nucleus and the Southern side there is plain Halo of comet but this part of Halo showed little darkening like a partial dimmer ring in side and the again increased in brightness near edge of Halo. We can see one faint star in the North-West edge of the Halo.
With unaided eye too comet was distinctly non-stellar, though can not see the disk but you can tell it is not like other stars but bit bigger.
While Abhir, Sagar & Nilesh were fighting with CCD camera drivers I pointed 12" to Moon, It was eye burning bright. I pushed magnification to the limit using Mead 2X barlow & TeleView 4mm Nagle. It was whopping 1975X !!! The overall appearance of moon image was blurry due to noticeable turbulence in eyepiece but for a moment air becomes steady a crisp view of moon crater made me feel like "I am flying over moon". Wow what a experience....
Photographing Comet:
Nilesh has two CCD cameras SBIG ST7 and Starlight Express HX9. But when we started setting up cameras we found that the drivers and softwares required for both Cameras are not installed on his laptop !!!, what a pain !!!! at 1:00 AM in night you discover you don't have drivers...... We assigned mission to Abhir to get drivers from Net and make it ready.... Thanks to nilesh wireless net access he searched on-and-on but did not find suitable drivers for HX9 camera.. Not even on manufacturers site!!!..
Mean while he found software and drivers for ST7 camera and it was up for use but we noticed that using ST7 is even more pain as we don't have finder scope and image download time for ST7 is much more.... for every image we need to wait for around 15 sec to download from camera, and as we need to do check and correct method for focusing it was taking too long time... We decided to use HX9 as it has very fast download time and also has live preview for focusing.
Abhir was still fighting on Net for drivers and finally with great efforts he found required drivers..... and at 4:30 AM HX9 camera was up and running....
We used off-axis guider with 0.7X focal reducer for HX9 camera...and thought off-axis guider may be useful for centering object on tiny CCD sensor with our Finderless Scope. But very soon we realize that CCD focus and off-axis guiders eye-piece focus are far far away from each other and now what left to us is "Shoot - Correct - Shoot" methodology for finding comet. The problem becomes more worse as we were using dew-shield for 12" which was making gun-point pointing almost impossible....
Even achieving focus was very painful it took us around 1/2 hr to get close focus, and it was just acceptable ( or rather i say we cant get better than that ). Then we started looking for comet with above said technique.....
We were trying and trying and trying but may be comet was upset with us and even we were trying in very small region of sky it was not ready to show up on Laptop screen....
All of us started getting more and more restless as time went by and we started worrying. If we had failed to image this comet then , it would have been a great shame on our skills of Observation, considering that we had such observatory level setup and years of experience in observing. But finally it appeared on the screen!
We were trying exposures of 2 secs as we know comet is very bright it would be easily get registered in 2 Sec too... We have taken hundreds of snaps during this search.... After fighting for almost 1hr with aiming finally we were able to nailed comet in CCD Field of view... what a relief... Then mount G11 tracked it smoothly for us....
We took series of exposure from 1sec to 30sec..... This comet is great photographically too, in photos it showed exactly what we saw in eyepiece.. I simply discarded my sketch which i did while observing comet...
After spending about 1/2 hr in photographing comet we decided to look for other object to capture on CCD, obviously the brightest object was M42 and we took few photos of Orion Nebula too.. The quality of photos was just acceptable again... may be CCD sensor was not in alignment with focal plane which caused some coma in all stars... But we were still happy as it was our first successful CCD photography session... (Only Nilesh did it before...) Later it was found that the focal reducer lens was full of thin fungus! That could have damaged the image too.
In the morning we saw Venus and Saturn and decided to end session. We dismantled and dumped everything in Nilesh's room (for him to put it back nicely later in day :) ).
I came back to mumbai by catching bus in the morning and sagar and abhir too left for their respective places in Pune.
After really a long time we have fun-filled and exciting Full Night Sky-Observation session...
And here are the photos.....
All these photos taken with same setup
Telescope : Mead 12" SCT with 0.7x reducer
Camera : Starlight Express HX9
Exposure : 2 X 2 binning, 2 sec, No Processing
Exposure : 2 X 2 binning, 5 sec, No Processing
Exposure : No binning, 30 sec , Brightness and contrast adjusted.
Exposure : 2 X 2 binning, 7 sec , No Processing
Nilesh with his 12" Mead on Losmandy G11 equatorial mount and ST7 CCD camera..
Sameer
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Comet,
Photography
