I didn’t expect to get any deep sky imaging in because of the full phase of the moon. I figured I do some tweaking on my system (I actually did some). Then, I got an email alert of a new comet suddenly brightening to naked eye visibility. I figured, what the heck… I’ll go out and see if I could see it. Well… duh…. I certainly could… it was right there… as if a new star had been added to the venerable constellation Perseus. Reports were indicating that the comet had brightened from mag 17 yesterday (this is beyond the reach of backyard telescopes) to mag 2 (easily naked eye visible). This is a 500,000x increase in brightness… for the mathematically challenged Maybe there was more to it than I’d expected? Only a look through the telescope would tell for sure.

I’d rebalanced the telescope earlier in the day, so I figured I’d do a quick 3 star alignment. I did this quickly and pointed the scope towards what I assumed was Comet Holmes. At low power (40x) there wasn’t any doubt that I was looking at a non-stellar object. A round, ‘fuzzy’ star. I quickly cranked up the power and a bunch of detail in the comet’s core was instantly visible. The core was a bit oblong and somewhat off-centered. It was also surrounded by a bright, hazy coma. This was a really sweet surprise

Ok, so this is an astro photography site, right. Well, I did post an image of the comet… though I spent a fairly sizable portion of my time outside glued to the eyepiece. The accompanying image was a 2 second exposure at prime focus using a Canon Digital Rebel XTi at ISO 100. I was shooting through my Astro Physics Starfire 160 refractor.

Because of the nature of the comet, I had some trouble getting properly focused initially. I decided to slew the scope over to nearby Capella in the constellation Auriga. This object was bright enough that I could get a good focus. Next, I slewed over to Mirfak in Perseus. This was the nearest star to comet Holmes. From here, I slewed and centered by hand. I took a variety of exposures from 1/4 of a second up to about 20 seconds. The longer exposures were completely over exposed… showing none of the comet’s inner details. A series of stacked shorter exposures likely would have been the best approach. This would have given me the short quick detailed images… that combined would have given me the larger extent of a longer exposure. Regardless, this surprise comet was a welcome treat. I’m not sure how long it’ll be visible (its currently visible all night long… rare for comets), but previous outburst comets have stayed visible for many weeks. I’m hoping that Comet Holmes will spend a bit more time with us as well.

Need more? Checkout Comet 17/P Holmes at higher power and Comet 17/P Holmes II.1 with some background stars. More recently, see how the comet has grown in Comet 17P/Holmes III.

Astro Photo Details:

* Designation: Comet 17P/Holmes
* Constellation: Perseus
* Magnitude: 2.5
* Size: 15′ (roughly 1/2 the diameter of the full moon!)
NOTE: Now roughly 30′… same size as the full moon

Astro Photo Processing Details

* Canon Digital Rebel XTi
* Astro Physics Refractor
* 18 x 75s exposures at ISO1600
* Stacked using RegiStax 4
* Neat Image
* Photo Shop Levels
* Gimp Levels

1. marlon, October 26, 2007:

   i am sure that this comet has been described by the sumerians very long before. i believed them, thats why when there’s suddenly a space phenomenon, i’m no longer surprised.

2. astrowan, October 27, 2007:

   WOW!!!!!

3. Martin, November 22, 2007:

   Does anybody have an idea how the sudden expansion has come about?

4. anthony, November 22, 2007:

   I’ve heard a number of possible theories on the comets strange
   behavior… but none claiming to be fact.
   The most logical is that as the comet freezes and thaws as it moves
   through the solar system, it does not always behave the same from
   orbit to orbit.
   The thought is that the comet could have fractured during this process
   and that it is now expanding as it travels.
   It could also have fracture (not destructively) and released
   previously unexposed materials.
   I guess these sound reasonable, although the comet has previously had
   ‘outburts’ in the past. Not quite to the extent of this one, but it
   has done stuff this before.

5. Denise Sutherland, January 18, 2008:

   Hi - what a great site but I can’t seem to find any other way to submit a comment or question. I found your site looking up the Canon XTi. I have been an amateur astronomer for a couple years now and adore looking at the beautiful photography I’ve seen. I just got a Rebel XTi for my birthday and can’t wait to start learning about astrophotography. I went to my local telescope store and purchased an FotoSharp focusing adapter (like a t ring that fits the Canon and gets perfect focus) for my new camera. Unfortunately I have spent the past couple days and another visit to the telescope store and can’t seem to figure out a problem. The focuser will not work on my new XTi. It is not a problem at all on the XT. What could be different about the XTi that it won’t work with the focuser? I suspect it is a focal point issue but we can’t figure it out. The autofocuser works on some focal points but not others. Strange and frustrating. Have you come across anything like this with your XTi. You seem to like yours a lot and you are obviously quite skilled. Any ideas? On another point, now that I am getting better at the astronomy I am looking to upgrade my scope to go with my new camera.. it never ends does it - it’s like an addiction. Any comments or suggestions would be greatly appreciated. I see that you are from the south where it seems the skies are always great. I am in Southern Ontario Canada and we have not seen a clear sky in a couple weeks almost. We’ve been getting lots of snow and everynight I am looking for a clear sky to no avail.

6. anthony, January 20, 2008:

   Hi Denise

   I’ve not tried using an autofocuser, yet. I do it the old fashioned, low tech way. I take advantage of the fact that my goto system is working well. I’ll slew to the object to be imaged… verify that its centered in the field of view… then slew to a nearby, bright star. At this point, I’ll pull out the eyepiece and hook up the camera. As the star is bright, I can see it well enough in the camera’s viewfinder to get a good focus. The, I’ll slew back to the object I planned to image a start shooting from there. I usually grab a quick (30 second) exposure just to verify that the object is in fact, centered in the camera’s field of view. I’ll make any required adjustments and then start acquiring the longer exposure images.
   Autofocus is on my list of things to do, but I just haven’t gotten to that part yet