60 replies to this topic

[sixela]

No, I mean "at the telescope side of the eyepiece".

When you put a filter between the eyepiece and the telescope, the angle of incidence of the light bundles is usually small (on my scopes less than 2.5°). When the filter is between the eyepiece and the NVD objective, the AoI varies between 0° for the on-axis object and 20° for an object at the edge.

Blueshift of the passband of a filter is roughly quadratic with the AoI, so the latter is 50 times worse ;-).

It may not matter for wide filters (a 12 nm filter will typically tolerate an AoI of 20° before an emission line goes off-passband), but for 2.5-7nm filters this is very important.

Edited by sixela, 12 August 2024 - 07:15 AM.

[robcac26]

No, I mean "at the telescope side of the eyepiece".

When you put a filter between the eyepiece and the telescope, the angle of incidence of the light bundles is usually small (on my scopes less than 2.5°). When the filter is between the eyepiece and the NVD objective, the AoI varies between 0° for the on-axis object and 20° for an object at the edge.

Blueshift of the passband of a filter is roughly quadratic with the AoI, so the latter is 50 times worse ;-).

It may not matter for wide filters (a 12 nm filter will typically tolerate an AoI of 20° before an emission line goes off-passband), but for 2.5-7nm filters this is very important.

Got it, thanks! Any input on which focal ratio range I should go with for the Baader H-alpha 3.5nm filter?

[sixela]

Depends on where the passband is, there is a bit of variation. I had one that was serendipitously redshifted so much that it worked until f/3.3 and even slightly lower. I've seen others that work optimally only down to f/4.5. So in general I'd say your best bet is a "regular" one down to f/3.8 and then an "f/3 highspeed", especially on scopes with a central obstruction (where everything has at least some blueshift.)

Here was the transmission graph for mine (measured with a friend and a suitable hi-res spectrograph):



That was a "regular" 3.5nm H-alpha Baader filter but frankly it almost looks like an f/3 highspeed.

But I've seen others with a similar passband but shifted almost 1.8 nm to the blue. These would work better on slow refractors but not as well on fast reflectors.

There have also been reports of "highspeed" ones that were much too redshifted, though (from a French reviewer, but can't find the reference).

Edited by sixela, 12 August 2024 - 04:18 PM.

[robcac26]

Depends on where the passband is, there is a bit of variation. I had one that was serendipitously redshifted so much that it worked until f/3.3 and even slightly lower. I've seen others that work optimally only down to f/4.5. So in general I'd say your best bet is a "regular" one down to f/3.8 and then an "f/3 highspeed", especially on scopes with a central obstruction (where everything has at least some blueshift.)

Here was the transmission graph for mine (measured with a friend and a suitable hi-res spectrograph):

Screenshot from 2024-08-12 23-03-05.png

That was a "regular" 3.5nm H-alpha Baader filter but frankly it almost looks like an f/3 highspeed.

But I've seen others with a similar passband but shifted almost 1.8 nm to the blue. These would work better on slow refractors but not as well on fast reflectors.

There have also been reports of "highspeed" ones that were much too redshifted, though (from a French reviewer, but can't find the reference).

Wow, thanks again. A lot of stuff there I hadn't even considered. I redid my focal ratio calculations, this time taking into account the central obstruction as well as the 1.15x effect from the SIPS coma corrector, and now I'm at these numbers:

1x - f/1.2
3x - f/3.6
67mm - f/2.13
55mm - f/2.59
31mm - f/4.60

I am also under the assumption that I'll usually be using this 3.5nm H-alpha filter for larger objects, so I probably won't be using the 31mm with this filter very often. That leaves just the 3x with a focal ratio slower than the 2.3-3.4 range (the middle of their three high-speed options), and even then it's just barely outside that range. The 67mm is just outside the range on the other end (2.13, just short of 2.3) but maybe the blueshift you mentioned from the central obstruction is enough to make it suitable, if I am conceptualizing it correctly?

So that leaves me with the <2.3 option being ideal for 1x and 67mm, the 2.3-3.4 option being ideal for only the 55mm by the numbers but just missing the 67mm and 3x by about 0.2 in either direction, and the >3.4 being ideal for the 3x and 31mm. Based on this I would think either the <2.3 or the 2.3-3.4 would be the way to go, and it looks like you're recommending the 2.3-3.4, or "f/3" as Baader refers to it. How much would I be missing out on if I use one of these filters outside of the recommended focal ratio? Or if there is variation in production is this whole thing a crapshoot anyway?

Sorry to keep bugging you with annoying questions, but hopefully someone in the future will be in the same situation and find this thread via the search feature and get the info they're looking for as well.

Edited by robcac26, 12 August 2024 - 11:36 PM.

[sixela]

For 1x a front-mounted filter will work but you’ll have bandpass shift in the edge of the field; it usually means that only 12 nm filters allow you to use the full 40° AFoV. But you can still use the central portion of the field of view effectively with more narrowband filters (I’ve seen a Chrona 3 nm filter with mild redshift and really high effective refractive index work well over an 18° AFoV, but that’s as good as it gets with 3.5-4 nm filters; others might work well in the central 10-12° only).

For 3x even a fairly narrowband filter can be used front-mounted without losing too much effective FoV because the edge angle of incidence is only 7°. But unless you buy a really large filter you’ll drop down to f/1.8 with 2” filters (27*3 mm for the focal length divided by 44 mm for the opening of the filter).

If you mount it between the 3x and the objective you can use a smaller filter and stay at f/1.2, but then you get the same bandpass shift as at 1x. You’re also likely to introduce some edge of field vignetting because the 3x converter is further from the PVS-14 objective, but that’s usually mild.

Watch out: “high speed” filters are and their target f/ratio are meant for conical light bundles, i.e. on the telescope side of the eyepiece or between the photocathode and NVD objective.

When used at an entry/exit pupil (front mounted on a 1x or 3x NVD) they will often produce a ring in the FoV with optimum transmission with worse transmission inside and outside and are tricky unless you really know what you’re doing or if they still work tolerably well at f/infinity (basically for the filter specs the field goes from f/infinity in the middle to really low f/ratio at the edge).

Don’t make the mistake to just calculate the f/ratio at the photocathode and use that for a filter used with parallel bundles through a pupil.

Edited by sixela, 13 August 2024 - 02:10 AM.

[robcac26]

For 1x a front-mounted filter will work but you’ll have bandpass shift in the edge of the field; it usually means that only 12 nm filters allow you to use the full 40° AFoV. But you can still use the central portion of the field of view effectively with more narrowband filters (I’ve seen a Chrona 3 nm filter with mild redshift and really high effective refractive index work well over an 18° AFoV, but that’s as good as it gets with 3.5-4 nm filters; others might work well in the central 10-12° only).

For 3x even a fairly narrowband filter can be used front-mounted without losing too much effective FoV because the edge angle of incidence is only 7°. But unless you buy a really large filter you’ll drop down to f/1.8 with 2” filters (27*3 mm for the focal length divided by 44 mm for the opening of the filter).

If you mount it between the 3x and the objective you can use a smaller filter and stay at f/1.2, but then you get the same bandpass shift as at 1x. You’re also likely to introduce some edge of field vignetting because the 3x converter is further from the PVS-14 objective, but that’s usually mild.

Watch out: “high speed” filters are and their target f/ratio are meant for conical light bundles, i.e. on the telescope side of the eyepiece or between the photocathode and NVD objective.

When used at an entry/exit pupil (front mounted on a 1x or 3x NVD) they will often produce a ring in the FoV with optimum transmission with worse transmission inside and outside and are tricky unless you really know what you’re doing or if they still work tolerably well at f/infinity (basically for the filter specs the field goes from f/infinity in the middle to really low f/ratio at the edge).

Don’t make the mistake to just calculate the f/ratio at the photocathode and use that for a filter used with parallel bundles through a pupil.

Hmm alright so how do I determine which one is optimal for handheld if I'm going to use a 2" filter front-mounted?

I also emailed Baader about this and just got a response. They said that for use with the telescope, since the light is hitting the filter before interacting with the eyepiece, the focal ratio of the entire system as I have calculated is irrelevant, and I just need to be more concerned with the telescope's focal ratio: f/4.5. Do you agree with that? If so, it seems for this purpose I should just go with the regular 3.5nm filter rather than one of the high-speed options.

As for handheld, it sounds like you wouldn't suggest a high-speed filter for that either if they are meant for light bundles that are already conical before reaching the filter. Does the focal ratio not matter since the light will be hitting the filter before anything else?

[sixela]

Hmm alright so how do I determine which one is optimal for handheld if I'm going to use a 2" filter front-mounted?

It's a game of compromises. I have a 12 nm filter for dark sites (to have the entire FOV in-band), a 6nm one for darkish sites (which has a high refractive index so I lose only the outer edge), and a 3 nm at home (where basically you need to filter really aggressively in the Bortle 8 sky or you really see a lot less).

I had a 2.5 nm Antlia with some red preshift, but its fairly moderate effective refracting index means that it's more prone to bandpass shift and it borders on the unusable at 1x (tunnel vision!)

Often I'll tend to use 3x and the front mounted 3 nm filter (or at dark sites a 4 nm dual band). Then you don't need to compromise and can get good emission line transmission over almost the entire FoV, but at a slightly higher f/ratio (because of the filter aperture which becomes the entry pupil), but f/1.6-1.8 is usually still not too shabby (except for the really faint and whispy stuff).
 

I also emailed Baader about this and just got a response. They said that for use with the telescope, since the light is hitting the filter before interacting with the eyepiece, the focal ratio of the entire system as I have calculated is irrelevant, and I just need to be more concerned with the telescope's focal ratio: f/4.5. Do you agree with that?

Yes. That's the virtue of putting the filter on the telescope side of the eyepiece in an afocal stack. You get conical bundles with the scope's f/ratio (usually a lot higher than e.g. at the photocathode) and very little variation in bandpass shift over the FoV. Which is the reason why my filter was also a "regular" one. It just happened (by chance) to also still work quite well in other use cases because of the mild preshift.

I know some people with faster scopes who preferred the "f/3" one just because it gives you better transmission when used front mounted at 1x over a large portion of the field, at the expense of its performance in their scope when used on the telescope side of the afocal stack...but frankly, I wasn't prepared to make that compromise (and it turns out the 'regular" one I bought was still preshifted a bit 'toward' f/3, although they aren't always).

At f/4.5 you're safe even for the "worse case" 3.5 nm regular Baader that I saw which had the bandpass slightly shifted the wrong way for fast scopes.
 

As for handheld, it sounds like you wouldn't suggest a high-speed filter for that either if they are meant for light bundles that are already conical before reaching the filter. Does the focal ratio not matter since the light will be hitting the filter before anything else?

When used front-mounted, the bundles are all parallel but when your object goes to the edge of the field the angle of incidence of the whole bundle increases, so that causes a bandpass shift just like a fast conical bundle. And for large true FoVs it's quite extreme. A 20° AoI corresponds to the extreme edge of an f/1.3 (!) conical bundle. The more you magnify, the less large the TFoV is, and the less it matters. At 3x, the 7° AoI at the edge coresponds to the extreme edge of an f/4 conical bundle (usually in the realm of the "not high speed" filters, although it can still be tricky for some Chinese 3-4 nm filters, but this will then typically only affect the extreme edge even for those).

Edited by sixela, 13 August 2024 - 03:44 PM.

[robcac26]

It's a game of compromises. I have a 12 nm filter for dark sites (to have the entire FOV in-band), a 6nm one for darkish sites (which has a high refractive index so I lose only the outer edge), and a 3 nm at home (where basically you need to filter really aggressively in the Bortle 8 sky or you really see a lot less).

I had a 2.5 nm Antlia with some red preshift, but its fairly moderate effective refracting index means that it's more prone to bandpass shift and it borders on the unusable at 1x (tunnel vision!)

Often I'll tend to use 3x and the front mounted 3 nm filter (or at dark sites a 4 nm dual band). Then you don't need to compromise and can get good emission line transmission over almost the entire FoV, but at a slightly higher f/ratio (because of the filter aperture which becomes the entry pupil), but f/1.6-1.8 is usually still not too shabby (except for the really faint and whispy stuff).

Yes. That's the virtue of putting the filter on the telescope side of the eyepiece in an afocal stack. You get conical bundles with the scope's f/ratio (usually a lot higher than e.g. at the photocathode) and very little variation in bandpass shift over the FoV. Which is the reason why my filter was also a "regular" one. It just happened (by chance) to also still work quite well in other use cases because of the mild preshift.

I know some people with faster scopes who preferred the "f/3" one just because it gives you better transmission when used front mounted at 1x over a large portion of the field, at the expense of its performance in their scope when used on the telescope side of the afocal stack...but frankly, I wasn't prepared to make that compromise (and it turns out the 'regular" one I bought was still preshifted a bit 'toward' f/3, although they aren't always).

At f/4.5 you're safe even for the "worse case" 3.5 nm regular Baader that I saw which had the bandpass slightly shifted the wrong way for fast scopes.

When used front-mounted, the bundles are all parallel but when your object goes to the edge of the field the angle of incidence of the whole bundle increases, so that causes a bandpass shift just like a fast conical bundle. And for large true FoVs it's quite extreme. A 20° AoI corresponds to the extreme edge of an f/1.3 (!) conical bundle. The more you magnify, the less large the TFoV is, and the less it matters. At 3x, the 7° AoI at the edge coresponds to the extreme edge of an f/4 conical bundle (usually in the realm of the "not high speed" filters, although it can still be tricky for some Chinese 3-4 nm filters, but this will then typically only affect the extreme edge even for those).

Awesome, so I will go for the not high-speed option at least for telescope use. Thanks for such detailed responses!

Sounds like if a different option would be better for handheld, you don't think it's enough to be worth buying another 3.5 filter just for that. Theoretically, how would you even determine which one would be ideal when front-mounted for handheld use since the light touches the filter first? If the focal length of the eyepiece receiving the light after it has been filtered doesn't matter for telescope use, does that mean the focal length of the PVS-14 (as well as the PVS-14 with the 3x) does not matter for handheld since it is also receiving the light after the filter? And if that's the case, how do you determine which speed to go with on this filter?

Edited by robcac26, 13 August 2024 - 04:19 PM.

[sixela]

The focal length does not matter. When front-mounted, the bundles are parallel, f/infinity, but only the on-axis object has zero angle of incidence.

You basically have to look at the manufacturer specs (or better, your own measurements) about how much a filter bandpass will shift and where the centre wavelength for zero angle of incidence lies.

You can of course assume that in general the central wavelength will be close to the emission line, but especially on cheaper filters it can wiggle up to 0.5 nm to 1 nm either way.

The blueshift for larger AoI is typically going to look like the one described in the Baader whitepaper here:

https://www.baader-p...ion_03Mai22.pdf

Note: for the effectiev refraction index, take 1.7 for cheaper Chinese filters (Optolong, some Antlia, Baader) and 2 to 2.1 for some of the more expensive ones (Chroma, some other Antlia, Astronomik MaxFR, Altair Astro).

It does mean that for really narrow filters (3 nm and 4 nm) there is going to be a tremendous amout of individual variation. I had to measure and return two Optolong L-Ultimate before I kept one (they don't come with individual test reports so it's Chinese roulette), and had to send one Antlia 2.5nm H-alpha back and then pick one from 5 other ones (with individual test reports from Antlia provided) to get a 'good' one.

I asked Altair Astro for an individual test report for a 4 nm dual-band and based my purchase on that, and I measured it and it matched the Altair Astro test report perfectly (and it works quite well).

This is an example of what you can produce once you test things yourself. This is the bandpass of an Altair Astro 4 nm around H-alpha measured at 0° and 7.66° angle of incidence (we did model using many other angle of incidence meeasurements), and a best fit model and effective refractive index for the blueshift with respect to angle of incidence:





This is what I'd call a really good filter: perfect centre wavelength placement for f/infinity, flat top at a really good maximum transmission, and a fairly high n_eff which keeps it working quite well even at f/3.72.

Edited by sixela, 13 August 2024 - 04:37 PM.

[sixela]

This is in the "not so good" category:




The max transmission is actually quite good (better than the replacement that I kept!) but it doesn't have a flat top and the centre wavelength is already blueshifted, and because the effective refraction index is lower it is more prone to blueshift, so it doesn't perform that well on my f/3.72 scope. At 7.66° (for the edge of the wavefront on my scope) there is 2 nm of blueshift, and you can see what happens if you move the first graph's bandpass to the left with respect to the emission line by 2 nm...

Obviously that one is really bad as a front-mounted filter. Even at 7° off-axis (at the edge of the FoV at 3x) you're well on your way out of the bandpass, and at 1x you're left with essentially zero transmission of H-alpha in the region more than 7.5° off-axis.

Edited by sixela, 13 August 2024 - 05:05 PM.

[sixela]

Just to show you how much variation you can have, this is another Optolong L-Ultimate:



This one is aggressively preshifted for fairly fast scopes (like mine) but not as much as to render it useless on slower scopes (although on an f/5 refractor it will do worse than the previous one!), is slightly wider, and has a slightly higher effective refractive index. So it's very good for use at 3x as a front-mounted filter. I even used it some of the time at 1x and the "tunnel vision" was somewhat bearable. It finally found a home in a friend's arsenal (PVS-14 NVD, f/4.5 scope).

[By the way: Optolong sells it as a "3nm" filter but really none of the ones I've ever seen are 3 nm filters unless you are prepared to round 3.9 nm --or in this case 4.2 nm-- to '3nm'.]

Edited by sixela, 13 August 2024 - 05:07 PM.

[sixela]

Just to show that on 6 nm filters you have much more leeway:


Sure, at 8° you have some blueshift but you're still well within the bandpass (in fact you haven't reached max transmission yet!) You can tolerate 4 nm of blueshift and still be in the passband (that's at well over 10° angle of incidence).

This thing still works without batting an eyelid on a friend's f/3 scope too.

[I redid measurements with a less noisy light source and the max transmission is actually 90.3% at n_eff is actually closer to 2, but I can't find those graphs; you get the gist here.]

Edited by sixela, 13 August 2024 - 05:25 PM.

[robcac26]

The focal length does not matter. When front-mounted, the bundles are parallel, f/infinity, but only the on-axis object has zero angle of incidence.

You basically have to look at the manufacturer specs (or better, your own measurements) about how much a filter bandpass will shift and where the centre wavelength for zero angle of incidence lies.

You can of course assume that in general the central wavelength will be close to the emission line, but especially on cheaper filters it can wiggle up to 0.5 nm to 1 nm either way.

The blueshift for larger AoI is typically going to look like the one described in the Baader whitepaper here:

https://www.baader-p...ion_03Mai22.pdf

Note: for the effectiev refraction index, take 1.7 for cheaper Chinese filters (Optolong, some Antlia, Baader) and 2 to 2.1 for some of the more expensive ones (Chroma, some other Antlia, Astronomik MaxFR, Altair Astro).

It does mean that for really narrow filters (3 nm and 4 nm) there is going to be a tremendous amout of individual variation. I had to measure and return two Optolong L-Ultimate before I kept one (they don't come with individual test reports so it's Chinese roulette), and had to send one Antlia 2.5nm H-alpha back and then pick one from 5 other ones (with individual test reports from Antlia provided) to get a 'good' one.

I asked Altair Astro for an individual test report for a 4 nm dual-band and based my purchase on that, and I measured it and it matched the Altair Astro test report perfectly (and it works quite well).

This is an example of what you can produce once you test things yourself. This is the bandpass of an Altair Astro 4 nm around H-alpha measured at 0° and 7.66° angle of incidence (we did model using many other angle of incidence meeasurements), and a best fit model and effective refractive index for the blueshift with respect to angle of incidence:

Screenshot from 2024-08-13 23-32-35.png

Screenshot from 2024-08-13 23-32-17.png

This is what I'd call a really good filter: perfect centre wavelength placement for f/infinity, flat top at a really good maximum transmission, and a fairly high n_eff which keeps it working quite well even at f/3.72.

This post has inspired me to take a deeper look at different manufacturers, especially now that I've determined I don't need one of Baader's specific high speed filters anyway.  From what I've read, it seems you can't go wrong with Chroma except for the price, and the Astronomik MaxFR seems to have excellent reviews as well, but maybe MaxFR isn't right for me since it's for faster focal ratios.  In the description for the MaxFR it says "very high contrast with no haloing" but the non-MaxFR regular one does not make that claim--is the MaxFR higher quality or is it the same thing just designed for faster scopes?  I might splurge for the Chroma 3nm since I'll of course be using this at home the vast majority of the time.  It says it's good for focal ratios down to f/4, so my f/4.5 falls in that range, but should I expect this to handle parallel light decently well too since it isn't made specifically for a narrow range of conical light paths? 

 

Is there a specific 685nm IR-pass filter you recommend over others or is there not much variation with those?

[sixela]

Regular Astronomik are also really good (the refractive index is a bit lower and the tolerance on centre wavelength placement is slightly relaxed, but at f/4.5 and for a 6 nm that’s really no issue).

But Astronomik doesn’t make really narrowband filters (they know what they can deliver on, and they’re hesitant to sell anything more narrow than 6nm; some Chinese vendors have just as much variation in bandpass setting and it does have an impact on performance but they don’t care).

Both my and Gavster’s Chroma have excellent bandpass centring and the highest effective refractive index I’vexever measured, and Gavster has been using them even for 1x photos with nebulae appearing fine up to 10° off-axis, but talking to Chroma that’s not what they _guarantee_ for _any_ filter.

Might want them to send you the batch’s test figures before you splurge on one (and order straight from them). You do want one with the emission line left of centre or dead centred in the passband.

If you’re interested I still have a 2.5nm Antlia that is really perfect for f/4.5 (it’s cherry-picked to have favourable preshift and I tested it myself) but slightly too narrow for my f/3.72, and I no longer use it since I have the Chroma.

But not really suitable for 1x viewing.

Not sure what shipping would cost if you’re in the US though. Send me a private message if you’d be interested, I’d rather prefer it to be used than sitting on my shelf.

Edited by sixela, 14 August 2024 - 02:34 AM.

[sixela]

As for an IR-pass: it’s much less critical. They will all work. I have an Astronomik.

For dark sites and galaxies you might want an Astronomik L1 as an IR _block_ by the way, to use only a passband without too much natural airglow (in IR there is a lot more airglow that reduces contrast, especially in periods with a lot of solar activity. Although these days when you have auroras even that filter doesn’t help ;-) ).

[Jethro7]

Hello Robcac26

Awesome offer by sixela. There will be questions from time to time but you will understand a whole lot more after first light. You will probably be too excited at the sights at first light to do much else, so on second light take the time to play around with different combinations of scopes, filters and eyepieces. 

 

HAPPY SKIES AND KEEP LOOKING UP Jethro

[robcac26]

This night vision stuff is awesome.  It kept me out so late last night I had to call out of work this morning haha.  I started out by taking out the 685nm filter and making an attempt to see Pluto for the first time, but it was behind a tree so I decided to check it out later and switched to the 3nm H-alpha.  I saw the North American Nebula, Veil Nebula, Bubble Nebula, Bow-Tie Nebula (all of which I had previously either never heard of or thought that I would only see them after a long road trip to a dark site) and views of the Ring Nebula, Dumbbell Nebula, and Andromeda Galaxy were much more pronounced than I've ever seen before.  I had no luck with the Pacman Nebula or the Elephant Trunk Nebula though.  I'm wondering if maybe those are too ambitious in Bortle 8/9 even with night vision, or maybe the 3nm is too narrow.  My 6nm should be delivered tomorrow so hopefully I'll be able to see if that makes a difference in the next few days.  I spent so much time checking out all those nebulae that by the time I finally went back to Pluto, it was too low in the sky and was behind a house.  It's great to have a whole new list of targets to be excited about, reminds me of when I first got into this hobby and was learning about all the different objects I could see from my house, except now that list is much longer!

[Speedy1985]

This night vision stuff is awesome.  It kept me out so late last night I had to call out of work this morning haha.  I started out by taking out the 685nm filter and making an attempt to see Pluto for the first time, but it was behind a tree so I decided to check it out later and switched to the 3nm H-alpha.  I saw the North American Nebula, Veil Nebula, Bubble Nebula, Bow-Tie Nebula (all of which I had previously either never heard of or thought that I would only see them after a long road trip to a dark site) and views of the Ring Nebula, Dumbbell Nebula, and Andromeda Galaxy were much more pronounced than I've ever seen before.  I had no luck with the Pacman Nebula or the Elephant Trunk Nebula though.  I'm wondering if maybe those are too ambitious in Bortle 8/9 even with night vision, or maybe the 3nm is too narrow.  My 6nm should be delivered tomorrow so hopefully I'll be able to see if that makes a difference in the next few days.  I spent so much time checking out all those nebulae that by the time I finally went back to Pluto, it was too low in the sky and was behind a house.  It's great to have a whole new list of targets to be excited about, reminds me of when I first got into this hobby and was learning about all the different objects I could see from my house, except now that list is much longer!

I told you it was going to be incredible, and you’ve just scratched the surface! Was this with your 11”? 

[robcac26]

I told you it was going to be incredible, and you’ve just scratched the surface! Was this with your 11”? 

Yep I did some handheld at 3x for a little while first and then attached it to the 11".  Looking forward to getting back out there again tonight!

[Speedy1985]

Yep I did some handheld at 3x for a little while first and then attached it to the 11".  Looking forward to getting back out there again tonight!

I figured based on the objects you described. If they’re not too low for your spot, try out M8,16, 17, and 20. 

[sixela]

 I had no luck with the Pacman Nebula or the Elephant Trunk Nebula though.  I'm wondering if maybe those are too ambitious in Bortle 8/9 even with night vision, or maybe the 3nm is too narrow. 

No and no, Pac-man is obvious even at 1x under a Bortle 8 sky with a 3nm filter.

 

The nebula in which the Elephant Trunk is located is also visible at 1x but very faint and less visible in light pollution (you sometimes miss it just because it's so large even at 1x!)

 

The Elephant Trunk itself is a lot smaller and fairly hard unless you have both a low enough effective f/ratio and enough magnification (it's really tough in anything smaller than a 10" scope, and the worse your sky, the more you need something large).

[robcac26]

I figured based on the objects you described. If they’re not too low for your spot, try out M8,16, 17, and 20. 

I believe those are all behind the line of trees behind my backyard, but there's a small gap between a couple of them, I'll see if I can time it right and get those in view.  If not, maybe my next astronomy accessory should be a chainsaw...

 

No and no, Pac-man is obvious even at 1x under a Bortle 8 sky with a 3nm filter.

 

The nebula in which the Elephant Trunk is located is also visible at 1x but very faint and less visible in light pollution (you sometimes miss it just because it's so large even at 1x!)

 

The Elephant Trunk itself is a lot smaller and fairly hard unless you have both a low enough effective f/ratio and enough magnification (it's really tough in anything smaller than a 10" scope, and the worse your sky, the more you need something large).

Hmm interesting.  I'll try the Pacman again, sounds like the Elephant Trunk might be out of reach here though.

[Speedy1985]

I believe those are all behind the line of trees behind my backyard, but there's a small gap between a couple of them, I'll see if I can time it right and get those in view.  If not, maybe my next astronomy accessory should be a chainsaw...

 

Hmm interesting.  I'll try the Pacman again, sounds like the Elephant Trunk might be out of reach here though.

I can see the nebula that the Elephant Trunk is located in at 3x from my yard using a 3.5 and 6.5nm, but not the trunk itself. The nebula is very faint as sixela mentioned. There are several others within that same area that are all visible as well, such as Cederblad 214, NGC 7822 & 7380 as well as the Pac-Man.

 

I feel your pain with the trees, a chainsaw would do wonders for me. 

[WheezyGod]

Awesome, thank you very much for the detailed response! I think I worded my last question poorly. I understand the specs are important, I was just curious if the specs would have an impact on which filter to use (for example if the 3.2nm Ha filter would be overkill if the SNR is above a certain level or something like that).

Here are the specs:

Resolution: 72
SNR: 36.9
FOM: 2656.8
EBI: 0.0
Halo: 0.7
Gain: 63,361
Photocathode Sensitivity: 2626
1 spot in zone 3

You mentioned viewing the planets with proper filters--is there any benefit to using night vision to observe the planets? And if so, by "proper filters" do you mean the same ones previously mentioned or are there others that should be used for this purpose?

Are these the specs of the device you received? If so those are insanely good if not the best I’ve seen on here. That SNR value is great, there’s been higher, but I’ve never seen a great SNR value with a perfect, 0.0 EBI.

There’s certainly been some debate about specs in the past around the importance of EBI vs. SNR for different types of objects and in different parts of the country that are typically hotter or colder where EBI becomes more important. One thing is for sure, holding your local viewing conditions aside, your tube will provide the best views of Ha/dark nebula. Particularly in the summer.

[robcac26]

Are these the specs of the device you received? If so those are insanely good if not the best I’ve seen on here. That SNR value is great, there’s been higher, but I’ve never seen a great SNR value with a perfect, 0.0 EBI.

There’s certainly been some debate about specs in the past around the importance of EBI vs. SNR for different types of objects and in different parts of the country that are typically hotter or colder where EBI becomes more important. One thing is for sure, holding your local viewing conditions aside, your tube will provide the best views of Ha/dark nebula. Particularly in the summer.

Yep that's the one I received, they said they had been holding it aside waiting for someone to place an order specifying that they will use it for astronomy purposes.  I guess I called at the right time!