Seeking advice for shooting Witch Head Nebula (IC 2118) - Forums

Topic starter

Feb 17, 2022 · Edited: Feb 17, 2022

I am gradually getting more involved in amateur astrophotography. I've done some nice acquisitions (haven't had time to upload more, I just have one uploaded now). I really like the Witch Head Nebula ( IC 2118 ). I want to make IC 2118 my next night of acquisition, but I am seeking some advice on getting some good sub-frames. What I am looking for specifically are some recommendations on exposure and ISO settings based on the past experience of others. I had some great results with the Flame and Horsehead nebulae with an exposure of 240s at ISO1600, but I have read that the Witch Head Nebula can be a little tricky. Weather conditions permitting, I intend to do about 2 hours of total acquisition.

I am currently using the following gear (I haven't found a money tree yet, so it's the best that is available for me):
Canon 90D (astromodified)
Canon 70-200mm f/4 L series (will probably shoot at 200mm @ f/5.6)
iOptron Skyguider Pro
ZWO ASI120MC-S w/ZWO mini guide scope
BackyardEOS, PHD2, Pixinsight 1.8.8-12

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Martin Doppelbauer

Feb 17, 2022

The witchhead nebula is notoriously difficult because it is quite faint and right next to a bright star (Rigel).
I have shot 2 min subs at ISO 400 with my EOS2000D.
See here: https://www.astrobin.com/va3yda/?nc=&nce=

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Brian Boyle

Feb 17, 2022 · Edited: Feb 17, 2022

Hi Crismus,

Welcome to the hobby.

The Witch Head is a much tougher target that the Flame/Horsehead - and it is starting to get a little late in the year, so you will have to chase it into the west.

The set you have looks fine for the Witch Head and the proposed sub-length is good to.

However, the critical thing for the Witch Head is the brightness of your sky.

I image from Bortle 3, and here is a 2hour image I took at f'5.5 (admittedly with a 100mm refractor) https://www.astrobin.com/ldtju1/?nc=&nce=

Here is an another image I took at 200mm but at f/2.5 in 3hours. https://www.astrobin.com/d2zf27/

I also tend to take slightly shorter subs, simply because I am always sky-limited, and CPU/disk space is not so much of an issue for me. More sub = better rejection as far as I am concerned. Also a tracking/guiding error results in the loss of a shorter exposure.

If you live in roughly similar conditions to mine, you should get something like the 1st image in terms of SNR, but closer to the 2nd in terms of resolution.

If you live in brighter sky conditions, it will be increasingly tough to get a decent image in 2 hours.

You may wish to leave the Witch Head for next year, when you can get a longer crack at it. There are some. lovely bright DSOs (Rosette, Seagull) just a little further to the East.

Good luck and clear skies!

Brian

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Crimsus

Topic starter

Feb 17, 2022

Brian Boyle:
I image from Bortle 3

Unfortunately I'm going to be at a Bortle 4 location. There are some darker areas around the region, but they aren't exactly safe at night (crime).

I actually did Rosette for Valentine's Day, so I've got that nebula covered for the year. Yeah, it is late in the year, but unfortunately weather, COVID, and other issues have prevented me from getting out to do shots in December.

Thank you for the info!

Brian Boyle

Feb 17, 2022

Bortle 4 is still pretty good….