The Cocoon and H beta filter

[Rustysplit]

My self and Si, simonfromsussex, tried in vain last night to find The Cocoon nebula using an Orion H beta filter. We were using my 14" f5 dob and a 27mm panoptic. The H beta filter is reported to work well on this target, but all we managed was " a possible hint of something there, what do you reckon?"

Anyone else managed to see this visually, and what did you use? Everything else, well nearly, was very good indeed last night.

[John]

I've had just one attempt at this object using my 12" dob and a 1000 Oaks H-Beta filter loaned to me by Mark at Beafort. I was using a 25mm eyepiece which I believe gives an optimum exit pupil for this filter. I had no more than you achieved although the sky at the time was not the darkest or most transparent I've ever seen it so I'm going to have another bash as soon as possible.

At least I've managed to pin down where to look !

[Rustysplit]

That is reassuring, if a little disappointing John, if you get my drift? We had high hopes having acquired "the magic bullet". It is something I will be chasing some more. We had shadowy glimpses of hints of something Looking forward to trying to bag the Horsehead with this filter too.

[John]

That is reassuring, if a little disappointing John, if you get my drift? We had high hopes having acquired "the magic bullet". It is something I will be chasing some more. We had shadowy glimpses of hints of something Looking forward to trying to bag the Horsehead with this filter too.

Thats my plan too Alan

I was a little disappointed about the Cocoon not "jumping out" but I ought to know better than that so I'll keep at it.

I'm expecting a tough time with the Horsehead even with the filter - people with larger scopes than mine have tried and failed to see it.

[Rustysplit]

Just been having a look at Luis' Cocoon images, I am now confident that we were in the right place. The slightly lighter patch of nebulosity and the dark cocoon section match what we could just about make out. I must admit to hoping that this would be clearer with the H Beta filter. If the sky plays ball at all this week, I am gonna have another crack at it, sat on the observing chair. Try and tease that detail out a bit.

[John]

Good luck Alan

I'll have another bash myself if the clouds co-operate.

I have to admin that I'm always in two minds over looking at images of an object before I'm confident I've seen it - I get concerned that "averted imagination" will strike

[Rustysplit]

I have to admin that I'm always in two minds over looking at images of an object before I'm confident I've seen it - I get concerned that "averted imagination" will strike

I know exactly what you mean John. It is difficult to trust your eyes only, and not let the brain fill in what isn't there. On the other hand, it can be useful to help you decide that you have been wasting your time staring at the wrong patch of sky for hours!!

[Moonshane]

I saw those pics too and wondered if it's possible. Anyone ever seen the California Neb with the same filter? Looks like we all have some late autumn/early winter targets with out Hb's!

[Rustysplit]

Not tried for the California yet Shane. I will certainly give it a shot though.

I set up outside as it was following the forecast and getting nice and clear after the rain, all cooled off, and now it's cloudy again!!

[crashtestdummy]

Did you find a decent supplier for the Orion hydrogen beta filter as last time I looked I couldnt find any stockists.

[Rustysplit]

I bagged it on ebay for £30, absolute bargain for a 2"

[John]

I bagged it on ebay for £30, absolute bargain for a 2"

Bargain indeed !

I had a look at one of the H-Beta's that Skies the Limit are advertising but when Alan sent it too me the data showed that it's transmission in the visual bandwidths was much less than the 92% claimed. More like 75% at max so possibly OK for imaging but no good for visual.

[Moonshane]

had a go at this tonight. found the right spot OK but the clouds defeated me and after about an hour of coming and going were winding me up. got the faintest hints of nebulosity occasionally with the 12" and Hb filter but will want to see it better to count it. the 25mm (55x and 5.4mm exit pupil) and the 20mm (69x and 4.3mm exit pupil) plossls were looking like they'd be productive.

[John]

I had the wrong scopes out tonight (4" and 6" refractors) otherwise I'd have had a go. The Cocoon seems to be a tough object to spot even with the H-Beta filter and 12"

[ollypenrice]

I haven't tried an H Beta on this but, from memeory, the darkened, starless dust lane opening into a rounder patch around the Cocoon was easy. Just no nebulosity! Curious. It isn't at all hard to image.

Olly

[michael.h.f.wilkinson]

I have had a go at it with a UHC filter, and my 80mm APM with 40mm Paragon, and later 22mm Nagler from Orpierre near Olly's place, on an extremely dark and clear night. I picked out the dust lane opening out to the round patch around the small group of brighter stars. What I noticed was a slight haze, especially in averted vision, almost like a bit of glare around the stars. The glare was absent from stars further out, and got worse when inserting the UHC filter (especially compared to other stars). This suggests it is not in fact glare, but a hint of nebulosity. I have noted similar effects in other faint nebulae (Flaming Star, California, Cave, Crescent).