IOM September 2009 – the Iris nebula in Cepheus

At last!  September has come around again and we can actually start imaging before 10:00 p.m. hooray!!  Less baggy eyes at work the next morning 🙂  This Month’s imaging object is the mysterious-looking NGC7023, a reflection nebula known as the Iris nebula in the constellation Cepheus.  From my notes I started imaging this one around 9:45 p.m. so not that much before 10:00 p.m. but sufficiently early in the evening for it not to feel too painful.

You need to go deep on this one in order to do justice to all the dark nebulosity that surrounds the Iris.  Look carefully and you’ll see a huge “clover-leaf” pattern surrounding the Iris nebula where most of the stars are missing – this is the massive dark nebulosity that fills this region.  In order to get that rich brown colour that is often associated with dark nebulae you need to go deep, and that means 5-10 minute sub exposures with the Hyperstar and 10-20 minute subs with an f#4.5 instrument like a Sky 90.  For total exposure times you’d like to get around 4-6 hours with the Hyperstar which translates to in excess of 24-hours with the Sky 90, which is bordering on silly.  This example shows the power of Hyperstar imaging where you can download quality data 6 times faster than is possible with a very popular imaging refractor.

The Iris nebula lies at a distance of 1,400 light years in Cepheus, and it’s not an easy one to process as the core is so bright it is hard to control it and not having it “blow out”, while at the same time trying to show the dark nebulosity at its best.  You’ll know you’ve got quality (deep) data and that you’re processing is top-notch if you manage to bring out the little pink region lying very close to the core of the Iris.

Hooray!!  The earlier evenings have returned – we now have (hopefully) another 7 months of great imaging ahead of us.

I wish you clear, dark, Moonless September skies.

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7 Responses to IOM September 2009 – the Iris nebula in Cepheus

  1. Malcolm Park says:

    A beautiful image of this dark nebular region. Particularly like the processing of the deep brown regions.

    I managed to begin imaging on the 3rd and 4th September (with Ha filter) by 21.40pm, capturing 5hrs of data each evening. These darker nights are welcomed! The thought of NGC7023 on my Sky90 for 24hrs would fill me with dread however my ambition this winter is to hook the new SXVR-M25C up to my Tak 180 ED with its reasonably fast f/2.8 optic. Unfortunately my Meade 12″ sct is not fastar compatible.



  2. Greg Parker says:

    Thank you Malcolm – Noel did a magnificent job on processing this, the brown dusty regions he brought out extremely well.

    The Tak 180 and M25C are a great combination and f#2.8 is plenty fast enough. I think you’ll find Starizona actually do make a Hyperstar III that is compatible with your Meade.


  3. Ian G says:

    Wonderful image, as always! I’m doing some of the similar imagery (with much more modest results, of course!) Did Iris at BFSP in Pennsylvania about a week ago. Some 1 hour of 5 min sub-frames. I have couple of technical questions.

    I see that you use a fork-mounted NS11 with Hyperstar, same as me. I have certain problems (sometimes) with the guiding. It seems that even decently polar-aligned (within 2-3 arc-minutes) scope would produce less than perfect stars, while guiding with 80mm WO and DSI-1 using PhD software. I was even contemplating to switch my mounting to a GEM. Now, seeing your setup I’m convinced that there are ways within it to improve (aren’t there always!).

    Also, I use SAC10 camera. It still works fine for me, though I’m thinking to switch to larger format one. What would be the better choice in your opinion?

    Clear Skies!

  4. Greg Parker says:

    Hi Ian,

    Thank you 🙂 Now there is a problem with the Celestron wedge (if that’s what you’re using) which I discuss in my “How to”” book “Making Beautiful Deep-Sky Images” by Springer. Basically the end of the wedge is an open ended box-section and it deforms as the scope swings about all over the place. I have mostly eradicated this problem by closing off the end of the wedge with some aluminium sheeting. You can find a picture of this, and what I’ve done somewhere on this site, probably under observatory, or projects. This almost completely cures the problem, but I think I also occasionally get problems in the field corners with what looks like coma, but is actually down to a lousy wedge. I am not sure about the SAC10 specs without looking it up – but for one shot colour I recommend the 6 megapixel M25C from Starlight Xpress, or if you are mono then the full frame H36. Hope this helps.


  5. Ian G says:

    Can’t find any pictures or description on this site. I will go ahead and order your book, however. I have a DIY wedge that is constructed from 20mm thick aluminum sheet – it was cut to my specs. I think it is sturdy enough. You can see it here:
    Also, take a look at the Iris Nebula, I’d love to hear your comments:


  6. Greg Parker says:

    Hi Ian,
    Your wedge is solidly constructed alright, but that open ended square section will give you problems. It takes very little flexure to throw out your polar alignment, and you have a very heavy mass (the C11) cantilevering all over the place. You need to close off that open ended box section with another aluminium plate to guarantee rigidity.
    The Iris image is very nice, some noise in the low signal regions, but this will go with more collected data – well done.

  7. Ian G says:

    Thanks, Greg, for your encouraging words!
    I will try to stiffen the wedge- I’m now thinking since I already have two 1/2″ threaded rods, on which the plate sits, I could connect them in couple of places. That should give me some additional rigidity. May be not the same as the full plate, but we’ll see if that would make any difference.
    Thanks again,

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