Tŷ Du Observatory

Everyone seems to be taking shots at Lulin at the moment but I haven’t had a clear night for weeks.  Sunday was my first opportunity to take a look at the green comet and  even though Starry Night showed it as being behind my house until after 11pm, it actually appeared in the gap between my house and the neighbours so I was able to image a little earlier than expected.

As the comet is moving quickly against the background I kept exposures to 20 seconds, which in hindsight was not long enough. I’ve spent hours trying to extract as much detail as I can from the 49 frames I took, but my best image is a stack of only 24.

Taken with the usual setup, 1200mm fl 254mm newtonian scope on EQ6 mount. Starry Night, EQMOD, Canon 300D (unmodded). Guided with 70mm cheapo scope using QHY5 guide camera.

As a footnote, I must try and get the Atik 16ic configured as my guider.  The QHY5 is so unreliable, both Guidemaster and PHD crash when using it. I have found that if I leave PHD with the error message on the screen it continues to guide regardless

In the same session I also managed to get a few 3 minute guided frames of M51.  I’ve not been able to get more than 1 minute subs previously, but the guider worked for most of the session, so I’ve been able to stack 20 frames to make this image:

It’s nice to have a colour camera to get these galaxy shots but I think I need to go longer than 3 minutes! Coma is very obvious even in this heavily cropped image – I think I may need to invest in a coma corrector next.

The sky cleared and the temperature dropped last night which gave me a few hours of viewing. I picked up Holmes 17P which is fading as the coma expands and got a few random shots while I waited for the rest of the eastern sky to move upwards into my field of view. I got some cluster shots before noticing Orion had slipped into the gap between my house and my neighbour which gave me a chance to image M42 in colour for the first time.

Tonight is clear again and I’m sooo glad I’ve got remote control working, it must be -4 centigrade out there and it’s been +14 all day. That takes some getting used to!

I left the camera while I completed a DVD quiz with the family and found nearly 500 frames of holmes when I finally got back to it. The result is interesting in that I think it shows some erratic movement in my mount, surely all the stars should show the same arc when I stack using the comet core as my target? Instead I have strange curves, take a look:

There not a lot of post processing gone into this, very little, so it’s a little rough around the edges.

I’m currently pointing the scope in the direction of the Perseus A galaxy which has several faint neighbours all within the SPC900NC’s tiny field of view.

I’ll come back to this post when I have more images, unless I freeze to the finder the next time I go out to realign everything.

I’ve just done a quick processing of this M1, my best yet but still room for improvement. The mount just won’t track for long periods I think it’s time I had the DEC axis apart for a regrease as well, or maybe I should leave it intact and adjust the grub screws, anyway that’s for another time. Here’s M1 taken from a stack of 28×40sec frames.

And another M42, this one is is taken from a stack of 200×2.5sec frames. When I get some time I’ll reprocess this with selective frames, but for now it’s just a rough draft.

There are more but I won’t have time to process them tonight so I’ll leave them for another day.

It’s currently very windy outside, but good seeing and only a few wispy clouds. I’ve been imaging Holmes(17P) again and have tried some trickery with image processing to bring out the internal structure of the comet nucleus. I’ve not had much success so far and after 45 minutes or so I slewed back to Mirfak and noticed the focus was out.  A quick trip out into the cold and everything is readjusted ready for the next avi capture.

Here’s a pretty version of the comet after some extreme processing. I can’t tell you how I got to this, It was “unsharp mask” and “find edges” mostly, but I think you’ll agree it doesn’t look like all the other comet photos on the web!

I’m still imaging, so hopefully there’ll be some better images before the night is over. Watch this space (excuse the pun).

It didn’t take long for my luck to run out. It’s about 1hour since the last sentence and the clouds have moved in. I’ve packed everything away as I can’t risk getting the equipment rained on while I’m sat indoors unaware of the changing weather outside.

I was in the process of moving to NGC457 the Owl Cluster in Cassiopeiae when I realized the poor image quality was cloud not misalignment. I managed 1 frame from an avi of 30 but even that has been smeared a little by the wind. I’ve imaged this one before, it may have been the first open cluster I ever found through the eyepiece, and still draws me back. When I’ve imaged this with a mono camera I had no idea that some of the stars were different colours, and this poor single frame doesn’t do the cluster justice.

I have produced another over-processed Holmes which emphasizes the compression artefacts as much as anything else, but I like it anyway.

I was out on Friday night (the 2nd) and managed to get a few new objects to add to the list. It was fairly clear with wispy high cloud, but as the night went on the dew became an issue with water running down the outside of the scope.

After taking the RA axis apart and reassembling I was keen to see if there was any difference but a hasty polar alignment I think was to blame for the image subject drifting up the screen with a slight zig-zag left to right. I recon if I can learn how to drift align I’ll be a lot closer now to getting longer exposures.

So I pointed the scope westwards, n-star aligned on Vega, Rasalhague and Altair then slewed to M27 for a quick check to make sure the goto was working. It was dead centre so I captured a few images here, then moved on to M57 as usual.

In order to find comet Holmes(17P) I needed to point the scope to the east which meant realigning the mount. This time I had a few problems trying to centre on some brighter stars as eastwards is over the top of my house which makes it difficult to get to the finder because of the angle. I settled on Mirfak, Algol and Almach but only after a lot of “left a bit, right a bit, up a bit ….” you get the idea, so I was surprised when I told the scope to goto the comet is was just off centre. I have a couple of images like this all taken from the same 100×10sec avi. I’ve been trying to reprocess the image to show some of the internal structure (see left) that others have been able to bring out, but so far there’s not much to see. The comet is so big only the heart of it fits into my feild of view with most of the surrounding gas and very faint tail cropped. Note the stars are elongated as the comet is moving at a different rate to the background.

As the scope was pointing eastwards I picked out some clusters that were missing from my messier chart, namely M35, M36, M37 and M38. The problem again is field of view, these clusters are too big for my small CCD. I spent some trying playing with EQMOD Mosaic but couldn’t put the pieces together. I think there was too much drift in each avi which makes the processed images smaller and therefore the edges don’t overlap as they should – if only I’d spent more time doing the polar alignment!!!

As the night went on, more objects emerged above the roof, I picked out Atlas and Merope in The Pleiades but couln’t see any nebulosity, I then moved on to a shot of Atik in Perseus before finally getting my first view of M1. I’d tried several times in the past to find M1 visually but with the long exposure set to 40 seconds I managed enough frames to give me my first photo, which as my old school teacher would say, “could do better”. It’s a start, hopefully the next time around I’ll be able to image this supernova remnant with a little more skill than I managed this time, but at least I can fill the space on my messier chart!

Mars had appeared by this time, but everything was soaking from the dew so I decided to pack up and dry everything off. Not a bad night, but I should make better use of the time between good nights to practice, learn and perfect the skills I need when the stars do come out. Next time…

The sky was clear all day, but I was worried that if I couldn’t get the mount to track I might miss a clear night. I visited a local auto repair shop in my lunch break and bought a tub of general purpose grease. The operating temperatures are -25 to +150 degrees C. Some articles on the subject of (re)greasing the EQ6 recommend special grease with operating temperatures as low as -50 degrees but I was limited by what was available to me.

 I stripped the RA axis whilst cooking our evening meal, so that after eating I could get on with applying the grease. To my surprise when I lifted the lid the grease was very dark in colour and I couldn’t help but laugh at the irony. Most people strip out the black (marmite) grease that used to come packed into the EQ6 gears and replace it with nice white synthetic grease, but I was replacing the white with the black.

Anyway, the point is whatever grease you use there should be enough to pack the bearing and tapered bearings at the base of the RA shaft were nearly grease free.

I stripped the shaft down as far as the worm and cleaned and regreased this, I then reassembled the mount and packed the tapered bearing before carefully inserting it back onto the RA shaft without getting black slime over everything. The operation complete I tightened the retaining bolt and the locking grubs.

Now for the fine tuning. I left the allen bolts finger tight on the worm housing and powered the mount. Performing a slew from left to right at speed 8 was accomplished without any unwanted grinding sounds so I slowed the mount down to 5 and tried again. It took a while before I realized the mount was moving – it’s very quiet now! I carefully tightened the allen bolts that hold the worm casing in place and tightened the small grub screws until they touched the internal stops. I didn’t want to apply any unnecessary pressure to the worm.

With the mount slewing I applied more pressure to the allen bolts until all were tight without. Next step – test it!

Imagine my disappointment when I finally carried the mount to the garden to find a number of large clouds rolling overhead. But I’m not easily put off and set everything up as there were gaps in the clouds so at least I’d get a chance to have another look at the comet.

I n-star aligned on mirfak, almach and algol which are all in the vicinity of comet Holmes(17P). I was trying not to slew the mount too far incase there was too much play in the RA axis. A goto on the comet put it just off centre and I started imaging my first sequence while I went indoors to take the controls remotely from a warm room.

The first and third images are stacked from 12 second exposures, the middle image is a stack of 2 second exposures to allow me to compare it with yesterdays results. No greenish hue visible today, infact I’d say more red if anything. The images have been stacked in registax with darkframe extraction but no post processing has been done on these.

I think my results are improved over yesterdays as I stacked the images by selecting a faint star rather than the comet as my alignment point.

I’ve just returned from realigning the scope in a westerly direction, Vega, Altair and Daneb as my 3 star alignment by the clouds seem to be getting worse. I want to see if there’s any improvement in the tracking now that the RA axis is properly lubed, but I may have to wait for another clear night before I have a chance to test this properly.