Simulations

[great_bear]

I'm not a sketcher - but here's two "simulations" (Gimp'ed Stellarium's) of exactly how two memorable sightings looked to me.

The Horsehead Nebula as seen through the viewfinder of my Mak180 (the viewfinder not the scope!! - couldn't see it through the scope itself!) and the owl nebula as it appeared through the Mak180 itself.

Both sightings in Devon (nr Bideford) in early December.

The Horsehead is really small and near the centre of the picture.

These simulations seemed like a good way for me to jog my memory of how I experienced particular sightings, so I thought I'd post them here, as they're quite realistic of how things looked.

I'll be doing more like this in future.

[yeti monster]

Rather neat. I've yet to nail horsey and am rather jealous that you got it in your finder!

[Doc]

You got the Horsehead in your viewfinder. Thats impressive, did you use a H-beta filter? How dark were your skies?

Nice sketches as well, well done.

[dweller25]

Wow, the Horsehead in a 50mm finder, I always thought it took a large reflector to see that.

[great_bear]

Wow, the Horsehead in a 50mm finder, I always thought it took a large reflector to see that.

Indeed - but it's all explained with a little bit of math. In my Mak180 the longest eyepiece (1.25") is 32mm. Since the scope is F15, this leads to an exit pupil of ~2mm even on this (widest-usable) eyepiece.

The viewfinder however, is 9x magnification. With 50mm of aperture, that's ~5.5mm exit pupil. Even a stonking great reflector doesn't get appreciably brighter than that (assuming average 44yr old eyes!). A big reflector will get you more magnification - but not especially brighter.

Thats impressive, did you use a H-beta filter?

No - there wer no filters involved. It was an accident. I was trying - or rather failing - to see the horsehead in the Mak180. I spent some considerable time looking for it and was getting nowhere. My final attempt was a failure, but I was using one of First Light Optics' USB adaptors attached to Carte du Ciel running on my Laptop and knew I was in the right place. Just I was giving up, I dolefully looked through the viewfinder to check I was lined-up to the right place and to double-check the position of surrounding stars, and thought to myself - "what's that thing there?" - it was just a reddish smudge almost imperceptable. Using averted vision I could make out some kind of definate shape but didn't know what it could be. I memorised the shape and location, and also the pattern of the surrounding stars.

It wasn't until a couple of days later I remembered the experience. I typed the date and time of the experience into Stellarium. Nothing made sense at first until I remembered that it was not the scope but the viewfinder that I had been looking through. I zoomed to the field-of-view that corresponds to 9x magnification with ~60 degree (my guess) AFOV.

To my amazement - not only did the stars immediately correspond to the right-angle pattern that I remembered so well from the evening, but the barely-visible smudge I saw was clearly labelled as the horsehead nebula.

Can I just be clear about something? The horsehead nebula is not the obvious red smudge in the simulated picture - it is the barely-visible shape that lies above it. Here it is the screenshot below clearly indicated with arrows in the picture for those of you not intimately familiar with the location of our horsey friend.

- I told you I tried to make this simulated images as accurate as real life!

How dark were your skies?

Very dark indeed - and my eyes were very-well dark-adapted. For the record this was at the Barton Court Health Spa near Bideford, Devon: A heavenly long weekend of private hot-tubs, massage, and astronomy (I let them know I was doing astro, lest their dogs get freaked out). It doesn't cost much either and the owners are very friendly.

A neighbour a few hundred-yards away had an annoying security light that kept popping on, but this stops happening later on in the evening.

I thought the dark skies late at night at Barton Court were excellent.

Nice sketches as well, well done.

Thanks - I basically recreate the view in Stellarium, and then spend some considerable time in "The Gimp" paint program adjusting brightness, colour etc., until the image gives exactly the same subjective impression I remembered from the eyepiece. Ironically, this makes these images more "accurate" (in the purely subjective sense) than photographs :-)

[great_bear]

One other experience of note from that evening (no image): That night I also saw a genuinely jaw-dropping view of the Great Nebula in Orion.

It looked startling enough unfiltered (SW Mak180 w/ Revelation 32mm Plossl), but when I attached an Ultrablock filter, the view was amazing.

Hubble-like wisps became clearly trailed around the nebula, leaving my guests stunned with amazement.

Possibly the best visual experience I'm likely to ever experience at the eyepiece?

[Doc]

I'm simply amazed, in all my time I've never heard that you are able to see this with what is basically the same as 10x50 binoculars. Well done it's something I'm going to have try next time I'm at a dark site.

[yeti monster]

That's it, from now on the bins will never leave my side.............

[DarkerSky]

That sounds like a lot of work you've put in there to get things as accurate as you could. Well done. I have seen the North American Nebula NGC 7000 with 16x50 bins from a dark sky site, but never the horsehead. Brilliant stuff

[dweller25]

GB - I tried with a 203mm F/6 Newtonian and a 32mm Plossl giving x38. That gave me an exit pupil of 5.3mm. BUT my skies north of Manchester are not good so I think that is what has helped you.

Well done, it's a rare achievement.