Horsehead hunting 2" vs 1.25" H-beta filter\eyepiece combos

[Stonius (Markus)]

I guess the other aspect of all this is the discussion of filters and conditions. My filter passes Ha, Hb and OII, so it's fairly broad - possibly making the detection of the horsehead more difficult compared to more specialised H-beta ONLY filters.


And even among Hb filters some are broader than others, with different peak transmission data. Am I correct in thinking that Lumicon is the go-to these days?



I've seen the horsehead through my 16" using the above-mentioned UHC filter, and in the same night, completely failed to see it through a 40" telescope (unfiltered) most likely because the sky had moved (as it does) and the horsehead was swimming in horizon muck.


I can imagine that it may well be in reach of a 12" instrument under good conditions , especially near meridian-crossing, with a quality dedicated H-beta filter.


Thanks Don. Now I have gear-lust again


Markus

[Don Pensack]

Originally Posted by Stonius

I guess the other aspect of all this is the discussion of filters and conditions. My filter passes Ha, Hb and OII, so it's fairly broad - possibly making the detection of the horsehead more difficult compared to more specialised H-beta ONLY filters.


And even among Hb filters some are broader than others, with different peak transmission data. Am I correct in thinking that Lumicon is the go-to these days?



I've seen the horsehead through my 16" using the above-mentioned UHC filter, and in the same night, completely failed to see it through a 40" telescope (unfiltered) most likely because the sky had moved (as it does) and the horsehead was swimming in horizon muck.


I can imagine that it may well be in reach of a 12" instrument under good conditions , especially near meridian-crossing, with a quality dedicated H-beta filter.


Thanks Don. Now I have gear-lust again


Markus

Lumicon doesn't currently make an H-ß filter since 2016.
The Go-To H-ß filters are Astronomik H-ß (since 2017) and TeleVue (since 2018). I had an Orion that measured 'very good', but variability in manufacturing means you might not get as good a filter, so caveat emptor.

At high altitude at 35°N, I see the Horsehead in the 12.5" without a filter, and a filter makes it easy. The main issue I had in finding it originally was that I was looking for something small, and it's about the same size as M2.

[Allan]

Originally Posted by ausastronomer

Allan,

While the Cone Nebula is a very challenging target in most amateur telescopes, it should be fairly routine in a 32" scope under Bortle 1 skies, particularly so, if you use a H-Beta filter. I've observed it at Ozsky, in all of the scopes we take to Ozsky from 14" to 30" at different times. It certainly isn't easy. One night we spent a good bit of time on it in my 18" scope. 3 of us could see it fairly comfortably with a UHC filter (Andrew Murrell, myself and Lance Humphries), yet another 1/2 a dozen people, including some experienced observers like Alan Dyer, could not see it. Hartung regularly observed it in his 12" scope, with a H-Beta filter. I would say it's definitely tougher than the Horsehead, but achievable in 12" scopes by skilled observers under ideal conditions. The planetary nebula that Andrew Murrell discovered (Murrell 1) is certainly a lot tougher and James Peirce, Andrew Murrell and I have observed that in James's 16" scope from Coonabarabran. The Cone Nebula certainly isn't a beginners target in a 12" scope, but I know at least 6 people personally who would be capable of it. I can guarantee you the worldwide list extends far beyond Don.

Cheers,
John B

I guess our eyes are target specific. I can tell you have trouble with the Horsehead. I would rate it a fairly basic observation in a 10” at SPSP. I’ve seen it there in my 5” refractor unfiltered. Even in my 3” refractor with a h-beta under Bortle 1 the Horsehead was a nice positive observation. The Cone is a significant step up from the Horsehead in difficulty.

[ausastronomer (John Bambury)]

Originally Posted by Allan

I guess our eyes are target specific. I can tell you have trouble with the Horsehead.

Our eyes are target specific for certain, as different people have different sensitivity to different wavelengths of light. That's an absolute given!

I don't know that I have that much trouble with the Horsehead. I've probably observed it close to, if not more than, 200 times over the past 40 years, which is when I gained access to telescopes 12" and over. For the 10 years I observed prior to that with smaller telescopes, I never bothered trying to observe it, as I had other programs I was focused on. I've probably only ever tried to observe it in a telescope under 12" less than 5 times. As nice as small refractors are, and they do give an aesthetically nice image, they don't have the light grasp, or resolution that I want to use these days. To be totally honest I spend very little time with telescopes under 14" these days. Even my 10" SDM, as nice as it is, generally only gets used for lunar and planetary observation, which is why I got Peter to build it. Ill be observing under Bortle 2 skies December new moon and will try for the Horsehead in my friends new 5" Triplet APO with a H-Beta filter.

Cheers
John B

[Stonius (Markus)]

Originally Posted by ausastronomer

Our eyes are target specific for certain, as different people have different sensitivity to different wavelengths of light. That's an absolute given!

Is there a way for the home user to measure this and generate a sensitivity curve for their own eyes? I'd be curious to be able to test in a setting that is not dependent on other variables such as transparency, filters, etc...


It's kind of a good thing to know, same as knowing your maximum pupil dilation.



Has anyone done this?


Markus

[ausastronomer (John Bambury)]

Originally Posted by Stonius

Is there a way for the home user to measure this and generate a sensitivity curve for their own eyes? I'd be curious to be able to test in a setting that is not dependent on other variables such as transparency, filters, etc...


It's kind of a good thing to know, same as knowing your maximum pupil dilation.



Has anyone done this?


Markus

Hi Markus,

I don't think this would be something easy to do at home. I may be wrong. It would be very easy to do in a laboratory that could emit light at various wavelengths and measure the response. Similar to doing a hearing test where they measure your ability to detect sound at a whole range of wavelengths and measure the lowest db level you are able to detect each of those frequencies.

I know its a real life thing because I have seen instances under very good conditions with large aperture, where a couple of observers have been able to observe the horsehead unfiltered very easily, yet a couple of other very experienced observers have not been able to detect it at all, due to their own eyes inability to detect the high red wavelengths emitted by IC434. However, on targets which emit at lower frequencies, they can go just as deep as the others.

Cheers
John B