Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

How To: Using your 2x (Galilean) binoculars as a booster to double the magnification of your regular binocs

Binoculars Collimation DIY Observing Planet Solar Moon
  • Please log in to reply
23 replies to this topic

#1 Helmut L

Helmut L

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 11 Sep 2021
  • Loc: Germany

Posted 16 October 2021 - 02:58 PM

Grazing through the threads in cloudynights I have found two guys who stated that they use their 2x binoculars as a booster for their main ones. I have one of the 2x54 Orions which I wanted to use with my 20x80 to get a magnification of 40x. I wasn’t sure, what to expect and it took me a bit to figure out how it works best, so I decided to share my findings here:

 

1. Mount your main binoculars on a tripod (or whatever you like best), so that you only have to handhold your 2x binocs.

 

Stargazing

 

2. Detach or fold back the eye cups of your main binocs in order to come as close as possible with the 2x binocs to the eyepieces. This way the field of view is as large as it can get. But make sure you cannot damage the objectives of your binoculars!

 

3. Shield your view from ambient light. A bino bandit for my 2x54 was one of my best buys.

 

Bino bandit
 

4. Refocus your main binoculars. Looking at a star at 40x it first seemed larger than Jupiter! The view resembled an unfocused telescopic one with diffraction rings around the star. Focusing the 2x54 didn’t help. After refocusing my 20x80 for observations with boosted magnification stars were pinpoint again. On the picture below you can see the difference in my marked focus points on the eyepiece (Position A: normal, B: boosted).
 

Focus Markings Eyepiece

 

5. Reduce your aperture. Looking at bright targets like Jupiter or Saturn chromatic aberration becomes much more apparent. My 20x80 is f4, so it is also apparent on bright targets without boosting the magnification. But in case of bright targets, you can spare some aperture to dim the light and also to raise the f-ratio. I tested with 60, 40, 30 and 20mm aperture masks and found that it works best with 30 or 40mm (see also my other post on how to attach aperture masks to your binoculars easily: https://www.cloudyni...our-binoculars/). Reducing the aperture of my 20x80 to 40mm results in 2mm exit pupils (EP) which magnified 2x results in an EP of 1mm(?) Maybe this is why 20mm won’t work for me, because this would result in only 0.5mm. The view is simply too dim and the resolution starts to decrease. Often it is said, that an EP of 0.75mm is the limit.
 

Aperture masks

 

6. Be aware that the field of view (FOV) will be drastically reduced. The 3.3° from my 20x80 is reduced to only 0.3°, but it’s possible to look around inside the FOV of the main binoculars. For small targets like the planets this won’t matter at all. Jupiter with its moons most often will fit 2 times in this small field. Also see the picture below, taken with my smartphone through the binoculars looking at the moon. Unlike the picture the 40x view was razor sharp, I simply couldn't come into focus with my phone. Also, the 40x picture only shows part of whats visible in the FOV.

 

Moon 20x vs 40x

 

7. What you can expect: Well, with 40x I could easily split the rings of Saturn from the planet and on Jupiter I could clearly see the North Equatorial Belt (NEB) at first glance. The SEB is harder but sometimes also possible. Sadly, I couldn’t see the shadow transits of the largest moons of Jupiter, Ganymede and Callisto, on the 4th of October, but the weather conditions were far from best. Looking at the moon, the detail of view is striking, but here you would wish for a larger FOV. But it’s a lot of fun observing the moon with 20x magnification and choose interesting craters to observe with 40x. Switching magnifications by holding your Galilean binoculars in front of your eyepieces only takes seconds. Furthermore, you could use this technique on the sun to double the size of sunspots. Sadly, boosting magnification only works well on bright targets. Dim deep sky objects get even dimmer. The targets here are possibly limited.

 

8. In case of problems, be sure to check the collimation of your binoculars. Slight miscollimation becomes more noticeable by boosting magnification resulting in two images your brain will not be able to merge anymore. The best way to check collimation is to defocus one eyepiece of your binoculars as far as possible. This way a star would look like a huge circle on one side, while it is pinpoint at the other side. If the pinpoint star is centered in the defocused star, your binocular is perfectly collimated and boosting the magnification should not be a problem. If it is outside the circle, then most likely boosting won’t work. In my case, the pinpoint star was in the middle between the center and the border of the star. So, my 20x80 isn’t perfectly collimated, but nevertheless works well with 40x magnification.
 

Collimation

 

Is there anybody who has tried this with 3x opera glasses or is willing to try? I’m now tempted to buy one just for usage as a booster because they are really cheap (50$). Also, 25mm opera glasses will fit perfectly into my eyepieces. Additionally, there are 4x12 monoculars much more expensive…

 

Clear skies
Helmut


  • spazmore, Astrojensen, Barlowbill and 2 others like this

#2 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 16 October 2021 - 04:14 PM

The dentist Galileans are great, but they are insanely expensive.  I would like a 4x roof binocular for boosting alone, but good ones don't exist.  The thing to keep in mind is that binoculars have mated objectives and eyepieces.  They are built to some tolerance, and collimated for that tolerance.  2x higher is not too far off and usually works well.  Binoculars these days tend to have 4-5mm of exit pupil as the sweet spot, so that gets reduced to around 2mm, a sweet spot for astro use.

 

My 25x100s get boosted the most often at night, right down to a 2mm exit pupil.  My 16x70s get boosted the most often during the day.  Sometimes I really want to see that eagle tear through fish guts!

 

I also find that for best performance, focus the booster at infinity, then focus the pair with the boosted.  The flatter field of the Orions helps a lot over the wonky field of the Vixens, but the Vixens are much sharper on axis.  As with all Galileans, the closer you get to the exit pupil of the boosted, the more the outer field matters.  The filter holders of my Oberwerk 25x100s get in the way, so I'm fine with the Vixens.  Putting bino bandits on the boosted helps with baffling.

 

Opera glasses are usually terrible.  They are meant for bright objects in big dark rooms, so their transmissions are not optimized for astro use.  I have yet to meet an opera glass I like, other than 2x astro binoculars, which work great at the opera.

 

Look for Saturn's moons.



#3 MT4

MT4

    Viking 1

  • *****
  • Posts: 924
  • Joined: 05 Jun 2021
  • Loc: Tokyo, JP

Posted 16 October 2021 - 11:30 PM

I've been able to use my Kasai 2x54 as a 2x booster for my 50x82 Kowa Highlander Prominar on Jupiter and Saturn, with great success.  The combo, at 100x, works well and allows me to see more features of the planets than what I can see in the stock 50x82 Kowa.  For example, I saw a Calisto transit the other night with this combo while in the stock 50x82 Kowa I failed to spot Calisto.

 

Like the OP and Butterfly, I focus the Kasai, which is really the same as the Orion 2x54 but in a different packaging, at infinity.  What's different is that for Jupiter and Saturn, I've found that I don't need to refocus my Kowa at all.  I'm terrible at focusing IF binoculars in general, so refocusing a 50x IF BT while holding the Kasai 2x54 in front of my eyes is more or less out of the question for me.  Since the resultant FOV is much reduced when using the 2x booster, I've actually only used the booster on Jupiter, Saturn and nothing else.  (I am not sure if using a 2x booster on the stars and getting a much reduced FOV is really worth it.   It might be a novelty and fun for a while though.)



#4 ECP M42

ECP M42

    Apollo

  • -----
  • Posts: 1,481
  • Joined: 28 Apr 2021
  • Loc: central Europe 45°N

Posted 17 October 2021 - 12:02 AM

You wrote well on collimation, focus and masks, good. 

 

I stacked two prismatics binoculars 10x, fixing them on a wooden board. Having a 100x in hand is a special experience, both on the moon and on animals during the day. So from 80m away I could see dry poop on the legs of a pigeon. Which I would never have been able to see at 10x or even 15x, even when fixed on the tripod. 

 

Henry


  • ButterFly likes this

#5 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 17 October 2021 - 02:39 AM

The beauty of nature is truly shocking at times.
  • ECP M42 likes this

#6 Cestus

Cestus

    Viking 1

  • -----
  • Posts: 583
  • Joined: 30 Jul 2019

Posted 17 October 2021 - 01:46 PM

I never thought to doing this. It really works? Now I'm going to have to look at some Orion's...and here I thought I was done.



#7 Stevenkelby

Stevenkelby

    Mariner 2

  • -----
  • Posts: 208
  • Joined: 01 Feb 2021
  • Loc: Adelaide Hills, South Australia

Posted 17 October 2021 - 05:30 PM

You wrote well on collimation, focus and masks, good. 

 

I stacked two prismatics binoculars 10x, fixing them on a wooden board. Having a 100x in hand is a special experience, both on the moon and on animals during the day. So from 80m away I could see dry poop on the legs of a pigeon. Which I would never have been able to see at 10x or even 15x, even when fixed on the tripod. 

 

Henry

Do you have any link or pictures Henry, I'd like to try that! 



#8 ECP M42

ECP M42

    Apollo

  • -----
  • Posts: 1,481
  • Joined: 28 Apr 2021
  • Loc: central Europe 45°N

Posted 18 October 2021 - 07:34 AM

No Steve, I don't have any photos or links.

 

But you have to use a SP roof binoculars to be able to observe the eyepieces of the other binocular.

It is not possible to do this with two Porro binoculars. And I had used a 10x40 Porro with a 10x25 pocket behind. Also a 10x50 Porro with a 10x32 roof behind (but heavier and more uncomfortable).

 

The possibilities are endless ... let your imagination run wild!

 

Henry


Edited by ECP M42, 18 October 2021 - 07:35 AM.

  • Stevenkelby likes this

#9 Helmut L

Helmut L

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 11 Sep 2021
  • Loc: Germany

Posted 19 October 2021 - 12:40 PM

I would like a 4x roof binocular for boosting alone, but good ones don't exist.

I have found these Pentax binoculars VD 4x20 WP, which seem quite interesting: https://www.amazon.c...&srpt=BINOCULAR

 

718g7-MiahL._AC_SL1500_.jpg

 

 

81dFIFQqYnL._AC_SL1500_.jpg

 

Never heard of a binocular consisting of two monoculars before, which you also can stack on top of each other. For me this seems like the ideal binocular for boosting, because it in itself is meant for boosting. Any thoughts on this? 

 

 

Look for Saturn's moons.

So far I only could see Titan. But I will try with Rhea, Tethys and Dione when they are the most elongated. Maybe I have to wait until the next opposition to have success.

 

 

I saw a Calisto transit the other night with this combo while in the stock 50x82 Kowa I failed to spot Calisto.

This is very sad. I very much hoped it would be possible to see the shadow transits even at 40x...

 

 

I never thought to doing this. It really works? 

This is exactly what I thought the first time I read about it. And as I tested it briefly at daytime the image was completely blurred, so I dismissed the idea immediately. Only when I found another guy who was boosting his binoculars too I was more determined to try. This is what led me to write this How To.

 

 

I had used a 10x40 Porro with a 10x25 pocket behind. Also a 10x50 Porro with a 10x32 roof behind

A 10x40 results in a 4mm EP. Magnified 10 times would it not be 0.4mm? Is this right? Seems a bit too small... Also, if you still have the 10x40, could you be so kind to check if they are perfectly collimated? I would have thought that at 100x magnification the slightest miscollimation would cause real problems merging the images...


Edited by Helmut L, 19 October 2021 - 12:43 PM.

  • Jon Isaacs likes this

#10 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 96,153
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 19 October 2021 - 12:49 PM

A 10x40 results in a 4mm EP. Magnified 10 times would it not be 0.4mm? Is this right? Seems a bit too small... Also, if you still have the 10x40, could you be so kind to check if they are perfectly collimated? I would have thought that at 100x magnification the slightest miscollimation would cause real problems merging the images...

 

That's right:

 

Exit pupil = aperture / magnification.

 

Jon


  • ECP M42 likes this

#11 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 19 October 2021 - 12:59 PM

I have found these Pentax binoculars VD 4x20 WP, which seem quite interesting: 

I bit.  Forty degree AFOV for a 10 degree field.  2.5 degrees when used as a 16x monocular.  I rekindled my admiration for Pentax with the Papilios at Petrified Forest National Park.



#12 ECP M42

ECP M42

    Apollo

  • -----
  • Posts: 1,481
  • Joined: 28 Apr 2021
  • Loc: central Europe 45°N

Posted 19 October 2021 - 04:40 PM

A 10x40 results in a 4mm EP. Magnified 10 times would it not be 0.4mm?

... at 100x magnification the slightest miscollimation would cause real problems merging the images...

Of course, Helmut. The pupil is 0.4mm and the total transmittance further lowers the amount of light coming out of the 100x40 binoculars. So the vision is not quite as clear as that typical of a 3x56 Galilean, but it works ... to do some experiments.
There is no collimation problem if both binoculars are collimated. But I don't remember if I had to correct the collimation by rotating one of the objectives to find the best sum (it is possible).
However, it is a good way to check the collimation of ours binoculars. 

 

This way of sum two binoculars to increase magnification has its positives, but it also has a lot of negatives. Including the loss of both light and field.
However, the fun is guaranteed, we can take away some curiosity and in some cases it is also possible to find an acceptable combination, to be used for some real purpose. But it is certainly preferable to have an instrument designed with that particular magnification that we need, or to have an instrument with interchangeable eyepieces to be able to vary at will without losing quality. 

 

If I had to reduce the AFOV of the Nikon 18x70 to 32°, to double its magnification, it would be cheaper to buy a Bresser SZ 12-36x70, which at least at 36x offers a decent AFOV of 60° ... smirk.gif

 

 

PS: I had already seen the Pentax VD 4x20 WP binoculars as soon as they came out and it immediately seemed interesting to me, but they have a very narrow vision, almost Galilean and they do not cost 30 €. 

 

Henry 


Edited by ECP M42, 19 October 2021 - 04:46 PM.


#13 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 19 October 2021 - 06:03 PM

Messier marathon with 2cm sounds fun though!  And 10 degrees with UHC filters stuffed in the eyecups as well.  My Visionking 5x25 blew apart, but they were fun while they lasted.



#14 MT4

MT4

    Viking 1

  • *****
  • Posts: 924
  • Joined: 05 Jun 2021
  • Loc: Tokyo, JP

Posted 19 October 2021 - 09:38 PM

This is very sad. I very much hoped it would be possible to see the shadow transits even at 40x...

 

 

The 50x82 Kowa is a wonderful instrument that has so far allowed me to see Titan and Rhea despite very challenging viewing conditions.  That said, 50x is still too low a mag for planetary viewing.

 

I wouldn't bank on being able to catch any moon transits at 40x.



#15 Helmut L

Helmut L

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 11 Sep 2021
  • Loc: Germany

Posted 19 October 2021 - 11:09 PM

I bit.  Forty degree AFOV for a 10 degree field.  2.5 degrees when used as a 16x monocular.  I rekindled my admiration for Pentax with the Papilios at Petrified Forest National Park.

 

by 2.5 degrees at 16x, do you mean apparent FOV or real FOV? 

 

Because this keeps me wondering: By boosting the magnification 4 times the FOV is only reduced by 75%?? Where did you get this information from?

 

What I experienced was that by boosting the magnification 2 times the FOV was drastically reduced from 3.3° to 0.3°, a reduction of 91%!! At 4x it would be even narrowed further.

 

Would be nice to know, what matters when it comes to boosting. My guess is that the smaller the objectives used for boosting, the greater the AFOV will be. So maybe the 2x54 Orions aren't the best tool.



#16 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 20 October 2021 - 04:22 AM

Entrance pupil is the concept here. Keplerian systems have a real entrance pupil at the objective, and a real exit pupil. Galileans are virtual. You would get the whole AFOV of the boosted pair with Galileans only if your eye's pupil were at the virtual exit pupil. But that's inside the body, so you can't. You are always too far away. It's not much different than placing your eye pupil far back from the eye relief position.

You can experiment with long eye relief eyepieces, Keplerian binos behind Kelperian binos, and Kelperian binos behind Galileans, in various combinations. Then try them all backwards. A beam expander (magnifier) in one direction is a beam reducer in the other direction.

Then consider non-boosted systems again. What happens to the TFOV when you stop down the objective of a Keplerian system? What about a Galilean system?
  • ECP M42 and Helmut L like this

#17 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 21 October 2021 - 02:39 PM

The 4x Pentax are interesting.  They are not going back immediately.  It boosts the APMs just fine, but their small AFOV limits the actual binocular field quite a bit.  I'll see how they do as scouts for the APMs, rather than the 8x42s.

 

Initial daytime impressions are that CA is under control, even at 16x, but the field wonks out about half way out at 4x.  I love the Japanese.  I have been chuckling for half and hour.  Made in China.



#18 faackanders2

faackanders2

    Fly Me to the Moon

  • *****
  • Posts: 7,129
  • Joined: 28 Mar 2011

Posted 21 October 2021 - 04:59 PM

Grazing through the threads in cloudynights I have found two guys who stated that they use their 2x binoculars as a booster for their main ones. I have one of the 2x54 Orions which I wanted to use with my 20x80 to get a magnification of 40x. I wasn’t sure, what to expect and it took me a bit to figure out how it works best, so I decided to share my findings here:

 

1. Mount your main binoculars on a tripod (or whatever you like best), so that you only have to handhold your 2x binocs.

 

 

 

2. Detach or fold back the eye cups of your main binocs in order to come as close as possible with the 2x binocs to the eyepieces. This way the field of view is as large as it can get. But make sure you cannot damage the objectives of your binoculars!

 

3. Shield your view from ambient light. A bino bandit for my 2x54 was one of my best buys.

 

 
 

4. Refocus your main binoculars. Looking at a star at 40x it first seemed larger than Jupiter! The view resembled an unfocused telescopic one with diffraction rings around the star. Focusing the 2x54 didn’t help. After refocusing my 20x80 for observations with boosted magnification stars were pinpoint again. On the picture below you can see the difference in my marked focus points on the eyepiece (Position A: normal, B: boosted).
 

 

 

5. Reduce your aperture. Looking at bright targets like Jupiter or Saturn chromatic aberration becomes much more apparent. My 20x80 is f4, so it is also apparent on bright targets without boosting the magnification. But in case of bright targets, you can spare some aperture to dim the light and also to raise the f-ratio. I tested with 60, 40, 30 and 20mm aperture masks and found that it works best with 30 or 40mm (see also my other post on how to attach aperture masks to your binoculars easily: https://www.cloudyni...our-binoculars/). Reducing the aperture of my 20x80 to 40mm results in 2mm exit pupils (EP) which magnified 2x results in an EP of 1mm(?) Maybe this is why 20mm won’t work for me, because this would result in only 0.5mm. The view is simply too dim and the resolution starts to decrease. Often it is said, that an EP of 0.75mm is the limit.
 

 

 

6. Be aware that the field of view (FOV) will be drastically reduced. The 3.3° from my 20x80 is reduced to only 0.3°, but it’s possible to look around inside the FOV of the main binoculars. For small targets like the planets this won’t matter at all. Jupiter with its moons most often will fit 2 times in this small field. Also see the picture below, taken with my smartphone through the binoculars looking at the moon. Unlike the picture the 40x view was razor sharp, I simply couldn't come into focus with my phone. Also, the 40x picture only shows part of whats visible in the FOV.

 

 

 

7. What you can expect: Well, with 40x I could easily split the rings of Saturn from the planet and on Jupiter I could clearly see the North Equatorial Belt (NEB) at first glance. The SEB is harder but sometimes also possible. Sadly, I couldn’t see the shadow transits of the largest moons of Jupiter, Ganymede and Callisto, on the 4th of October, but the weather conditions were far from best. Looking at the moon, the detail of view is striking, but here you would wish for a larger FOV. But it’s a lot of fun observing the moon with 20x magnification and choose interesting craters to observe with 40x. Switching magnifications by holding your Galilean binoculars in front of your eyepieces only takes seconds. Furthermore, you could use this technique on the sun to double the size of sunspots. Sadly, boosting magnification only works well on bright targets. Dim deep sky objects get even dimmer. The targets here are possibly limited.

 

8. In case of problems, be sure to check the collimation of your binoculars. Slight miscollimation becomes more noticeable by boosting magnification resulting in two images your brain will not be able to merge anymore. The best way to check collimation is to defocus one eyepiece of your binoculars as far as possible. This way a star would look like a huge circle on one side, while it is pinpoint at the other side. If the pinpoint star is centered in the defocused star, your binocular is perfectly collimated and boosting the magnification should not be a problem. If it is outside the circle, then most likely boosting won’t work. In my case, the pinpoint star was in the middle between the center and the border of the star. So, my 20x80 isn’t perfectly collimated, but nevertheless works well with 40x magnification.
 

 

 

Is there anybody who has tried this with 3x opera glasses or is willing to try? I’m now tempted to buy one just for usage as a booster because they are really cheap (50$). Also, 25mm opera glasses will fit perfectly into my eyepieces. Additionally, there are 4x12 monoculars much more expensive…

 

Clear skies
Helmut

I bought opera glasses for all my daughters.  They were on sale and looked nice had clear optics but were heavy.   They had a handle at the side so you could keep your hands and arms lower for a play, show, or game.  I know at least one of them used them for plays.



#19 Helmut L

Helmut L

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 11 Sep 2021
  • Loc: Germany

Posted 24 October 2021 - 09:04 AM

The 4x Pentax are interesting.  They are not going back immediately.  It boosts the APMs just fine, but their small AFOV limits the actual binocular field quite a bit.  I'll see how they do as scouts for the APMs, rather than the 8x42s.

 

Initial daytime impressions are that CA is under control, even at 16x, but the field wonks out about half way out at 4x.  I love the Japanese.  I have been chuckling for half and hour.  Made in China.

Could you be so kind as to measure the TFOV when used 4x compared to 16x? And also the TFOV of your APMs with and without boosting? Would be nice to know if the field is reduced by 75% or rather much more.



#20 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 24 October 2021 - 02:47 PM

Could you be so kind as to measure the TFOV when used 4x compared to 16x? And also the TFOV of your APMs with and without boosting? Would be nice to know if the field is reduced by 75% or rather much more.

The stars I got in from initial testing through breaks in the clouds was 9 degrees with room to spare in Cygnus.  I can see each eyepiece when boosting the APMs, but the narrow field is restricting the binocular overlap.  I'm waiting for less cloudy and Moony nights for astro testing, especially with filters.  The field does much better at night.  I notice slight changes around half the field, with quite decent performance out to about three quarters.

 

The APMs have an AFOV of around 65 degrees at 16x.  With an AFOV of 40 degrees at 4x, I can't see all of the APM's AFOV, but only 40 degrees of it (it's a Keplerian booster so its AFOV is still determined by the booster's eyepiece).  So I get 40 degrees of the 16x view, for a TFOV of around 40/16, or 2.5 degrees.  A equivalent way is to consider 40 degrees of the 65 degree field with the APM's TFOV of about 4 degrees ~ 40/65 * 4.  The actual binocular field, where there is overlap, for my IPD, is about half of that.  If your are closer together, you can get more overlap.  If the AFOV of the Pentax were larger, I would also get more overlap.  It is what it is.

 

The 2.5 degree field is about the same as when the bino halves are stacked, but the color correction is better.  It's not terrible when stacked, but I'd only do that in the context of a Messier marathon, or if I really had to.  For CA, I tested a bare steel power line section against a blue sky.  That's always a severe test.  The CA is there, but surprisingly under control.

 

I had a daytime trip out to Grand Canyon with them.  They make a lovely scout for the 16x.  No Condors, a few Hawks, and plenty of Ravens.  The vultures are gone already.  Boosting the APMs is much better than stacking the bino halves.  I did reasonably well hand boosting with the 16s on a monopod.  CA is still unnoticable when boosting the APMs.  The lentil of overlap becomes unnoticable after a minute or so, and they become nice 64x70s.  Working with two sets of IF can be challenging, but most targets for the 16s are far enough away that changing focus isn't needed.

 

Saturn and Jupiter when boosted should be very telling.  In Cassiopeia, I should get a very good estimate of the TFOVs.  For filters, 1.25" filters do not fit in the eyecups.  I can place them in the objective shields, but they will fall out when horizontal.  I don't see that getting in the way for upward looking.  Hopefully, sometime this week.


  • ECP M42 and Helmut L like this

#21 ButterFly

ButterFly

    Mercury-Atlas

  • *****
  • Posts: 2,709
  • Joined: 07 Sep 2018

Posted 28 October 2021 - 02:15 AM

The APMs have an AFOV of around 65 degrees at 16x.  With an AFOV of 40 degrees at 4x, I can't see all of the APM's AFOV, but only 40 degrees of it (it's a Keplerian booster so its AFOV is still determined by the booster's eyepiece).  So I get 40 degrees of the 16x view, for a TFOV of around 40/16, or 2.5 degrees.  A equivalent way is to consider 40 degrees of the 65 degree field with the APM's TFOV of about 4 degrees ~ 40/65 * 4.

Past me is an idiot who forgot the factor of four!  They are 4x binoculars.  It's about a 37.5' field rather than a 2.5 degree field when boosting the APMs.  I boosted on the Pleiades tonight.  I fit from Alcyone to Taygeta with a little room to spare.  They are 38' apart.  Just a monopod today, so no real planet testing.

 

The 4x Pentax themselves just fit from Caph to Ruchbah, about 9.75 degrees apart.

 

Fixing the nonsense above, the Pextax see about 10 real degrees of the APMs 65 degree AFOV.  The 10 real degrees of the Pentax, at 4x, turn into the 40 degree AFOV of the Pentax.  The total magnification is 16*4 = 64x.  The 40 degree AFOV of the Pentax is at 64x, so the TFOV is about 40/64 = 0.625, or 37.5 minutes.  That makes better sense as an approximation.

 

The 4x themselves were actually quite nice.  No M33 naked eye tonight.  The field is okay out to about 3/4 from the middle.  It's decent after that.  The North America nebula was showing unfiltered, as well as the backbone of Cygnus.  I tried two Lumicon UHCs in the objective "dew shields".  They didn't fall out when looking at Auriga, which was still low.  The Flaming Star region was doing great.


  • Helmut L likes this

#22 Helmut L

Helmut L

    Lift Off

  • -----
  • topic starter
  • Posts: 13
  • Joined: 11 Sep 2021
  • Loc: Germany

Posted 29 October 2021 - 03:41 PM

ButterFly, thank you very much for all your thoughts on this matter. Very much appreciated!

 

From all you are saying I gather that Keplerian binoculars are better for boosting than Galileans, because the FOV will be larger. 

 

So, in my case the FOV I would get using the 4x Pentax for boosting my 20x80 would be actually larger than the one I get with the 2x Orions (0.5° compared to 0.3°). Now that's something!

 

But I am not so sure if 4x isn't a bit too much for boosting my f4-binocs considering CA and alignment issues. Sadly one wouldn't find any Keplerians with magnifications below 4x. So, if you want to boost by 2x or 3x you have to stick with Galileans. 



#23 MT4

MT4

    Viking 1

  • *****
  • Posts: 924
  • Joined: 05 Jun 2021
  • Loc: Tokyo, JP

Posted 01 November 2021 - 11:24 PM

ButterFly, thank you very much for all your thoughts on this matter. Very much appreciated!

 

From all you are saying I gather that Keplerian binoculars are better for boosting than Galileans, because the FOV will be larger. 

 

So, in my case the FOV I would get using the 4x Pentax for boosting my 20x80 would be actually larger than the one I get with the 2x Orions (0.5° compared to 0.3°). Now that's something!

 

But I am not so sure if 4x isn't a bit too much for boosting my f4-binocs considering CA and alignment issues. Sadly one wouldn't find any Keplerians with magnifications below 4x. So, if you want to boost by 2x or 3x you have to stick with Galileans. 

There’s the highly rated Zeiss 3.5x13 Theatis.   I’ve entertained thoughts of buying it to boost my 50x82 Kowa.  If the mag were 2.5x I would bite.

 

3.5x is bit high, but perhaps not too high to boost a 32x82 Kowa.  Hmmm.. this might be the over-100x I’ve been looking for without having to buy the APM 120/Oberwerk 127.



#24 ECP M42

ECP M42

    Apollo

  • -----
  • Posts: 1,481
  • Joined: 28 Apr 2021
  • Loc: central Europe 45°N

Posted 03 November 2021 - 02:35 AM

You cannot use the CZJ Theatis 3.5x15, because the objectives will be closer than the eyepieces. SP roof prism binoculars or Galilean binoculars only. Or two monocles (also Porro-prism) adapted ad hoc.

 

but the magnification is the right one for ... 

 

 

ps: With the Zeiss Diadem you can (3.6x).


Edited by ECP M42, 03 November 2021 - 02:43 AM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Binoculars, Collimation, DIY, Observing, Planet, Solar, Moon



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics