Observing with Smaller Apertures: 130mm and Below

[Ray of LIght]

I observe with a 102mm/4 inch fast refractor and wondered about the best maximum  lunar/planetary magnification I can attain if I use a specific filter.

[Mak the Night]

2 hours ago, Ray of LIght said:

I observe with a 102mm/4 inch fast refractor and wondered about the best maximum  lunar/planetary magnification I can attain if I use a specific filter.

That's an interesting question. I think a lot will be to do with how aggressive the filter is, the particular colour if it is a Wratten, and the exit pupil for your scope. I don't think ND or neodymium filters would hinder high magnifications. On my 102mm Mak I found a Wratten #12 Yellow was fairly successful viewing the Moon in daylight/twilight conditions at around 170x. Yet I thought the #21 Orange revealed more detail even though it only has a 46% transmission rate compared to the 74% of the #12. The #80A Blue (30% transmission) was good for lunar/planetary on my 102mm Mak and 130mm Newtonian and I've successfully used it at 250x on the 130mm.

I've been using a Wratten #11 Yellow Green filter (78% transmission) on my 130mm reflector with a fair bit of success at high magnifications on Mars and Saturn (200x, 250x, 257x).

In fact, with this Barlow/7mm combination I can and have been getting 257x with my 130mm and the #11 which is near its resolution limit. Conditions need to be decent though.

However, I couldn't even find the target (Mars) when using this light red filter (above) when using my 130mm. At 25% transmission I knew it wouldn't be easy but TS Optics include the #23A in their filters for scopes 130mm and under set. A 130mm refractor might be OK.

I had a similar problem with this #15 Deep Yellow (67% transmission), but at least I found the target! It may have worked better if the conditions were above average. The #8 Light Yellow worked very well on Mars and the Moon at 200x and 250x.

[Ray of LIght]

11 hours ago, Mak the Night said:

That's an interesting question. I think a lot will be to do with how aggressive the filter is, the particular colour if it is a Wratten, and the exit pupil for your scope. I don't think ND or neodymium filters would hinder high magnifications. On my 102mm Mak I found a Wratten #12 Yellow was fairly successful viewing the Moon in daylight/twilight conditions at around 170x. Yet I thought the #21 Orange revealed more detail even though it only has a 46% transmission rate compared to the 74% of the #12. The #80A Blue (30% transmission) was good for lunar/planetary on my 102mm Mak and 130mm Newtonian and I've successfully used it at 250x on the 130mm.

I've been using a Wratten #11 Yellow Green filter (78% transmission) on my 130mm reflector with a fair bit of success at high magnifications on Mars and Saturn (200x, 250x, 257x).

In fact, with this Barlow/7mm combination I can and have been getting 257x with my 130mm and the #11 which is near its resolution limit. Conditions need to be decent though.

However, I couldn't even find the target (Mars) when using this light red filter (above) when using my 130mm. At 25% transmission I knew it wouldn't be easy but TS Optics include the #23A in their filters for scopes 130mm and under set. A 130mm refractor might be OK.

I had a similar problem with this #15 Deep Yellow (67% transmission), but at least I found the target! It may have worked better if the conditions were above average. The #8 Light Yellow worked very well on Mars and the Moon at 200x and 250x.

Great information Mak! I suppose my 102 f5.9 Meade has many advantages and disadvantages. Unless I use a Barlow it is difficult to attain high magnifications. My 3.2mm Starguider, un-Barlowed, gives me 187x. I can reach much higher magnifications up to it's 204x stated usesble limit (if you go by the 50x per inch per conditions formula), and higher with a 2 or 3x BarIlow. It seems that the the #11 yellow-green, the #8 light yellow and the #80A blue look like they might be good candidates to test. Do they sound like a good fit for the 102 frac? The X-Cel 2x Barlow seems like a good one, according to my research, perhaps you can let me know how you like it if you have had a chance to give it a good run! I see you have already used it with your 7mm X-Cel.

[ronin]

For magnifications I see 2x diameter often quoted but personally I suspect that the previous idea of 1.5x diameter is a much more realistic value. Meaning that to me something like 150x is your maximum.

I will also throw in that if the scope is fast, as you say, then maybe less again. Fast scopes are more difficult to produce and so tend to suffer more aberrations. A fast lens is in a way just too "Spherical" to produce a good image. So rule or no rule or whichever rule you want to choose the lens just will not do it.

[Mak the Night]

2 hours ago, Ray of LIght said:

Great information Mak! I suppose my 102 f5.9 Meade has many advantages and disadvantages. Unless I use a Barlow it is difficult to attain high magnifications. My 3.2mm Starguider, un-Barlowed, gives me 187x. I can reach much higher magnifications up to it's 204x stated usesble limit (if you go by the 50x per inch per conditions formula), and higher with a 2 or 3x BarIlow. It seems that the the #11 yellow-green, the #8 light yellow and the #80A blue look like they might be good candidates to test. Do they sound like a good fit for the 102 frac? The X-Cel 2x Barlow seems like a good one, according to my research, perhaps you can let me know how you like it if you have had a chance to give it a good run! I see you have already used it with your 7mm X-Cel.

187x is still a pretty good planetary magnification though. A lot depends on conditions and the actual target. Only a few years ago I could sometimes see Galilean moons with the naked eye from my back lawn. Jupiter was high in the south east the last time IIRC. The past couple of years the seeing hasn’t really been up to it though. I think the #11, #8 and #80A should be fine for high magnification. Yellow, green and blue are shorter wavelengths than the longer red/orange light wavelengths. I’ve often wondered if some of the shorter colours/wavelengths are just more penetrative.

Violet     380–450 nm     
Blue     450–495 nm
Green  495–570 nm     
Yellow 570–590 nm     
Orange 590–620 nm     
Red      620–750 nm

With my 130mm reflector, once I’ve found the target in the RACI, I have to re-acquire it in the eyepiece. As the EQ2 RA and declination controls can be a little awkward for me, and they aren’t really that precise, this can entail some fiddling about to find what I’m looking at and get it in focus. The Light Red filter seemed too dark to find the target (Mars) and I eventually lost patience and switched filters. This probably won’t be such an acute problem on a refractor though. I’ve wondered if it’s some peculiarity of red light that makes it difficult like this, plus the filter only has a 25% transmission rate.

I’ve been daylight testing the #11 Yellow Green. This is not a longpass filter but is apparently used for colour correction in some photography. It does work well on Saturn at high magnifications. I had up to 257x last night, although admittedly the transparency was not good. I could still see cloud detail and the Cassini Division. The #11 does seem to make daylight cloud detail easier to see, as do yellow contrast filters in general and the 80A Blue and 82A Light Blue filters. Jupiter may be visible for me from around 21:30 tonight (below), if there’s enough clear sky I would like to try the 82A. It would be interesting to view the GRS with the 82A. I'm guessing the clouds won't let me play though lol.

The X-Cel Barlow seems fine. I’m pretty sure you can unthread the element but I haven’t attempted this yet lol. It works well with the X-Cel EP’s and I’m not detecting any vignetting. I like the undercuts on both the Barlow and eyepieces, they aren’t problematical with compression rings but do stop the draw tube pulling straight out of anything. This is useful on the Bazooka as being a Newtonian on an EQ the focuser is often pointing downwards. The set screw isn’t as firm as I’d like, but it does its job well enough. I tested it with a deliberately loose set screw and the X-Cel eyepiece undercut catches it well enough. Considering my disability, I find the X-Cel EP’s and Barlow easy to manipulate and use. They seem ergonomically well designed to be used at night in cool conditions. I have some problems keeping my core temperature up, so something easy to hold and manipulate whilst shivering is a plus. The X-Cel series is generally well liked. I can see why.

[Mak the Night]

Today looks like serious pants weather, but there are indications that next Tuesday might be OK. Maybe a chance to see a twilight Saturn. Mars and Jupiter might be still visible for me. And there is the Moon.

Above: Saturn at Transit 22:20, 12/7/16 (17.3°, Ophiuchus) . Plenty of time to prepare then lol.

[Ray of LIght]

7 hours ago, Mak the Night said:

Today looks like serious pants weather, but there are indications that next Tuesday might be OK. Maybe a chance to see a twilight Saturn. Mars and Jupiter might be still visible for me. And there is the Moon.

Above: Saturn at Transit 22:20, 12/7/16 (17.3°, Ophiuchus) . Plenty of time to prepare then lol.

Raining pants and dogs here too right now, lol! I will PM, but having some pretty serious medical issues, hopefully temporary, which may make night observing a little difficult for a few more days. I just hope the trees don't ruin my chances to get to Saturn and Mars. I will get to the Sun, as soon as it makes an appearance! I expect my TV Sol-Searcher today or tomorrow. That should make my solar observing life a lot easier! I will let you know how it works; read good things about it. I hope the weather works out for you, please let me know how it goes.

 

[Mak the Night]

4 hours ago, Ray of LIght said:

Raining pants and dogs here too right now, lol! I will PM, but having some pretty serious medical issues, hopefully temporary, which may make night observing a little difficult for a few more days. I just hope the trees don't ruin my chances to get to Saturn and Mars. I will get to the Sun, as soon as it makes an appearance! I expect my TV Sol-Searcher today or tomorrow. That should make my solar observing life a lot easier! I will let you know how it works; read good things about it. I hope the weather works out for you, please let me know how it goes.

 

It is July, right? lol I'm going to try to be optimistic about the weather.

EDIT: Now the BBC Mendacity App says I may have an hour from 22:00 clear.

If I can get a decent view of Jupiter I'll try the #82A at 200x and 250x to compare it with the Baader Neodymium.

No GRS though.

[Ray of LIght]

23 hours ago, Mak the Night said:

It is July, right? lol I'm going to try to be optimistic about the weather.

EDIT: Now the BBC Mendacity App says I may have an hour from 22:00 clear.

If I can get a decent view of Jupiter I'll try the #82A at 200x and 250x to compare it with the Baader Neodymium.

No GRS though.

How did you make out Mak? I received my #47 violet filter and the TV Sol-Searcher. Just trying to figure out a good way to mount it. I found my extra Quickfinder base so I may use it as a base also to raise up the Sol-Searcher so it is not blocked by my dew shield. Double sided sticky tape seems to work well and I will be leaving it installed anyway. It is quite small. Be back in a bit.

[Ray of LIght]

1 minute ago, Ray of LIght said:

How did you make out Mak? I received my #47 violet filter and the TV Sol-Searcher. Just trying to figure out a good way to mount it. I found my extra Quickfinder base so I may use it as a base also to raise up the Sol-Searcher so it is not blocked by my dew shield. Double sided sticky tape seems to work well and I will be leaving it installed anyway. It is quite small. Be back in a bit.

Oh, on the intended base! 

[Mak the Night]

3 hours ago, Ray of LIght said:

Oh, on the intended base! 

Looks interesting Ray. I'd like to see a #47 close up, it is sometimes referred to as a Deep Blue filter I think.

I was set up by around 21:00 and got organised and let the scope cool for nearly 45mins before I got a view of a setting Jupiter at 200x. The transparency wasn’t brilliant and it was still basically daylight/twilight but I could see the equatorial cloud belts quite well, although there wasn’t a huge amount of detail. The four moons were visible, if a bit hazy, strung out in a line just like in the screenshot from CDC. I’d only taken four filters out with me; the neodymium, #82A, #11 and #8. I tried the #82A Light Blue on Jupiter at 200x and I didn’t think it really did much for it. Whether it was the transparency, or the fact that the background sky was still blue at that time, I don’t know. I switched to the Baader Neodymium and thought that it did improve clarity and contrast on surface features compared to the #82A. I didn’t try the #8, so that will be next time if I get a chance as it is supposed to be good for the belts.

By about 22:15 Mars was quite visible, as usual the #11 and #8 helped with viewing maria that could be seen, although the difference with the neodymium was subtle, I think the #11 made the maria I could make out a bit darker. Both the #82A and the neodymium made the northern polar cap slightly more distinct. Although I think the neodymium had the edge slightly. I observed Mars at 200x and 257x. The filters appeared to work the same at both magnifications with no degradation at 257x. In fact, I thought I could see more detail at 257x.

Saturn was a bit hazy at 257x although I could easily see Titan, some cloud detail and the Cassini Division were visible. I stepped down to 200x and then to 128.5x (basically the 7mm X-Cel without the Barlow) as it was easier to reacquire the target in between changing filters. I think I’d nudged my RACI and it was a bit out although I normally routinely check it, especially before a twilight session when I have some daylight to check it with a low power EP (32mm Plossl). At 128.5x I viewed Saturn (now moving a lot slower lol) with no filter, and then with the #11, #8, 82A and neodymium in that order. As usual the #11 seemed to enhance the Cassini Division and the cloud detail, as did the #8 to some extent. There wasn’t a whole lot of difference between the neodymium and the 82A it seemed to me though. The 82A having a slight edge over the Baader Neodymium for cloud/surface detail, but neither were as good as the #11 for making the Cassini Division more distinct. I did think the surface cloud was a little bit easier to see with the neodymium than without any filter though. I packed up around 01:00.

 

[Ray of LIght]

•   

  1 hour ago, Mak the Night said:

  Looks interesting Ray. I'd like to see a #47 close up, it is sometimes referred to as a Deep Blue filter I think.

  I was set up by around 21:00 and got organised and let the scope cool for nearly 45mins before I got a view of a setting Jupiter at 200x. The transparency wasn’t brilliant and it was still basically daylight/twilight but I could see the equatorial cloud belts quite well, although there wasn’t a huge amount of detail. The four moons were visible, if a bit hazy, strung out in a line just like in the screenshot from CDC. I’d only taken four filters out with me; the neodymium, #82A, #11 and #8. I tried the #82A Light Blue on Jupiter at 200x and I didn’t think it really did much for it. Whether it was the transparency, or the fact that the background sky was still blue at that time, I don’t know. I switched to the Baader Neodymium and thought that it did improve clarity and contrast on surface features compared to the #82A. I didn’t try the #8, so that will be next time if I get a chance as it is supposed to be good for the belts.

  

  By about 22:15 Mars was quite visible, as usual the #11 and #8 helped with viewing maria that could be seen, although the difference with the neodymium was subtle, I think the #11 made the maria I could make out a bit darker. Both the #82A and the neodymium made the northern polar cap slightly more distinct. Although I think the neodymium had the edge slightly. I observed Mars at 200x and 257x. The filters appeared to work the same at both magnifications with no degradation at 257x. In fact, I thought I could see more detail at 257x.

  

  Saturn was a bit hazy at 257x although I could easily see Titan, some cloud detail and the Cassini Division were visible. I stepped down to 200x and then to 128.5x (basically the 7mm X-Cel without the Barlow) as it was easier to reacquire the target in between changing filters. I think I’d nudged my RACI and it was a bit out although I normally routinely check it, especially before a twilight session when I have some daylight to check it with a low power EP (32mm Plossl). At 128.5x I viewed Saturn (now moving a lot slower lol) with no filter, and then with the #11, #8, 82A and neodymium in that order. As usual the #11 seemed to enhance the Cassini Division and the cloud detail, as did the #8 to some extent. There wasn’t a whole lot of difference between the neodymium and the 82A it seemed to me though. The 82A having a slight edge over the Baader Neodymium for cloud/surface detail, but neither were as good as the #11 for making the Cassini Division more distinct. I did think the surface cloud was a little bit easier to see with the neodymium than without any filter though. I packed up around 01:00.

   

  
  
  
  
  
  
  
   
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• You were using the bazooka i assume? You're right, the #47 does look bluish violet. Will take a picture, it is a GSO (like the others I have bought lately). Pretty well made. The TV Sol-Searcher is very well made. I'm glad you got some good observing and testing in. I will probably try my #82A, #11 and #8 also. I will try the new #47 on the Sun, along with the Sol-Searcher (will have to align it a bit I'm sure) maybe tomorrow. Will be almost 90 degrees! Good thing I got the solar finder! I've been thinking about also trying out the Polarizing filter set I bought on solar. Looking forward to getting out at night, hopefully soon. Testing gear on the Sun is great, but not the same. Back in a bit.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
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[Mak the Night]

Yeah, the Bazooka is fairly simple to set up. I've been leaving the polar oriented mount/tripod at the bottom of the garden covered in a plastic bag and a couple of bin bags to protect it from the rain and elements. This way I only have to carry the OTA and a couple or three eyepieces out with me if I get a window of opportunity. After over a year of using the 102mm Mak I've realised the extra 28mm of the Bazooka makes a lot of difference. Plus, the Bazooka won't dew, even if my filters do occasionally lol.

[Ray of LIght]

Figured. If you ever sell it, I will buy it! Took a picture of the #47. Very dark but may be perfect for our nearest Star!

[Ray of LIght]

I think I mounted the Sol-Searcher ok. I don't think I will use the stock red dot so I may remove it. The Sol-Searcher and Quickfinder should be fine! Let me know what you think.

[Stu]

Looks good Ray, hope you get some sun soon!

[Ray of LIght]

18 minutes ago, Stu said:

Looks good Ray, hope you get some sun soon!

Hope so! Will be hot but I think should be ok after the humidity drops. Thanks, glad I found the spare Quickfinder base!

[Mak the Night]

48 minutes ago, Ray of LIght said:

Figured. If you ever sell it, I will buy it! Took a picture of the #47. Very dark but may be perfect for our nearest Star!

The Bazooka's beautifully simple; a couple of mirrors in a tube lol! All Wiki says about the #47 is it is a Blue Tricolour. Used for colour separation. Complements #29 and #61. I don't think it's a longpass.

It's made me wonder about blue filters in general though. Shown here: A Baader Neodymium, three 80A filters and an 82A. The neodymium appears to have a blue tint. As blue is between 450–495 nm these filters must allow that wavelength through and effectively block higher and lower. The neodymium seems to have many similar properties to a blue filter.

It's way too anorak for me to figure out though lol.

[Mak the Night]

34 minutes ago, Ray of LIght said:

I think I mounted the Sol-Searcher ok. I don't think I will use the stock red dot so I may remove it. The Sol-Searcher and Quickfinder should be fine! Let me know what you think.

It looks kinda cool. I'm not sure what it does, but it looks the part. lol

[Dave In Vermont]

Indeed! Your Meade 102mm F/5.9 is the best-dressed short refractor out there. The TV solar-finder adds quite an attractive image. I'm sure you'll be delighted at how easy it will be to put our star dead-on in your eyepiece. I know how simple it became when I attached my Helio-Pod to my scope, which employs the same design as your TV Sol-Searcher.

Form & Function!

Dave

[Ray of LIght]

Thanks Dave! Glad you found our new discussion. I'm sure Mak knows what the Sol-Searcher does. The aperture directs the captured Sun towards the little screen on the other disc and theoretically it should be at least close to the eyepiece. It has alignment adjustments. Believe me, I don't know much myself. Pretty sure I will remove the red dot finder and clean up my OTA. 

[Mak the Night]

19 minutes ago, Ray of LIght said:

Thanks Dave! Glad you found our new discussion. I'm sure Mak knows what the Sol-Searcher does. The aperture directs the captured Sun towards the little screen on the other disc and theoretically it should be at least close to the eyepiece. It has alignment adjustments. Believe me, I don't know much myself. Pretty sure I will remove the red dot finder and clean up my OTA. 

It looks impressive Ray. I'd consider an RACI for nocturnal use as well. The shoe behind the Telrad looks like it will accept standard Synta feet. I doubt I could use any of my scopes without an RACI with my disability.

https://www.amazon.com/Orion-7211-Right-Angle-Correct-Image-Finder/dp/B0000XMVDG/ref=sr_1_fkmr0_1?ie=UTF8&qid=1467842996&sr=8-1-fkmr0&keywords=6x30+Right-Angle+Correct-Image+Finder+USA

[Ray of LIght]

 I have a GSO 8x50 RACI in my Agena wishlist! Is that one any good? It says it has a dovetail mount, looks like what I have. I could take the Quickfinder on and off as needed. Something tells me the RACI will help my horrible back pain. I will check out your link also.

[Ray of LIght]

Actually the one you linked to me is less expensive than the GSO. Is the 6x30 better for me do you think? The RACI would help with my back issues.

[Mak the Night]

14 minutes ago, Ray of LIght said:

Actually the one you linked to me is less expensive than the GSO. Is the 6x30 better for me do you think? The RACI would help with my back issues.

I'm pretty sure my Orion 9x50 is GSO. 

It's about half the aperture of my Skymax! The 9x50 has a 5° FOV which is about 10 Full Moons. Oddly, the Orion 6x30 I use on my 90mm Mak has a 7° FOV, which is about 14 Full Moons. To be honest, I think the 6x30 would be all that was needed on any scope under 200mm. Once you've used an RACI you wonder how you did without one.