Barlow for imaging the Moon?

[Ken Mitchell]

Hi all,

I'm looking for recommendations on barlows for imaging. I'm using a 72mm refractor with asi120mcs and would like to take close ups of the Moon's surface without changing the scope.

Is this possible with barlows or are they only for observing?

If so, is there anything worth buying for around $100-$150?

 This is my latest image, 2 mosaic form 2x 4000frames.

As you can see there is some detail in it but not as much as I like.

Thanks

Ken

[vineyard]

That's a beautiful mosaic.  I'll defer to others far more experienced, but I recently used a 2.5x Powermate with my 72mm refractor - just for visual, but it was great and since it doesn't change the focus (much) it might be easier than a Barlow - there's no reason I couldn't have taken a photo with that (other than just laziness at the time!)?  Cheers.

[CraigT82]

That's a really nice image! I personally use the 2x and 3x explore scientific focal extenders and I find them both excellent 

[Owmuchonomy]

The place to start with this is to work from your camera pixel size (3.75 microns); times that by 4 or 5 and aim for that f/ratio.  So the sweet spot for your camera is around f/ 15 to 19.  Choose a Barlow or Powermate that gets you in that region.  The other way you can increase the level of detail (without changing scope) is to switch to a Mono camera used in conjunction with an IR pass filter.  My best Moon images (see link below) were obtained with either an ASI174 or ASI290 mono camera.  The 290 has particularly good near IR sensitivity.

[Ken Mitchell]

3 hours ago, CraigT82 said:

That's a really nice image! I personally use the 2x and 3x explore scientific focal extenders and I find them both excellent 

Do you refer to this one?

https://www.astroshop.eu/barlow-lenses/explore-scientific-barlow-lens-focal-extender-2x-1-25-/p,54035

 

Does a focal extender like that introduce vignette or softness in the corners?

Ken

[CraigT82]

7 hours ago, Ken Mitchell said:

Do you refer to this one?

https://www.astroshop.eu/barlow-lenses/explore-scientific-barlow-lens-focal-extender-2x-1-25-/p,54035

 

Does a focal extender like that introduce vignette or softness in the corners?

Ken

I've never had any problems with mine.

[Ken Mitchell]

12 hours ago, CraigT82 said:

I've never had any problems with mine.

Is there any advantage choosing the 2" before the 1.25"?

Ken

[Ken Mitchell]

22 hours ago, Owmuchonomy said:

The place to start with this is to work from your camera pixel size (3.75 microns); times that by 4 or 5 and aim for that f/ratio.  So the sweet spot for your camera is around f/ 15 to 19.  Choose a Barlow or Powermate that gets you in that region.  The other way you can increase the level of detail (without changing scope) is to switch to a Mono camera used in conjunction with an IR pass filter.  My best Moon images (see link below) were obtained with either an ASI174 or ASI290 mono camera.  The 290 has particularly good near IR sensitivity.

That's interesting, thatks. So the best one would be a 2.5x or should a regular 2x be ok?

I found the Baader Hyperion 2.25x or the ES focal extender 2x(What Craig recommends) The 2.5x Powermate is just a bit high in price.

Any thought on those?

Ken

 

Edited February 10, 2020 by Ken Mitchell

[CraigT82]

14 minutes ago, Ken Mitchell said:

Is there any advantage choosing the 2" before the 1.25"?

Ken

For planetary and lunar imaging with small sensor cameras... no.  The 2" is just extra weight (and the 1.25" ES extender isn't exactly lightweight!)  I would only consider the 2" for visual use with 2" eyepieces, or if you wanted to switch to a DSLR to image the moon - in this case you may get some vignetting with a 1.25" barlow and the larger DSLR sensor.  

[Ken Mitchell]

Update:

So I recently purchased the Explore Scientific x3 focal extender. Done some tests with it and must say I'm very pleased with its performance.

My biggest concerns were softness and vignette in the corners but I can't see any of those in the images I took.

Here are some examples taken with the barlow+72mm apo and zwo asi120mcs

Ken

 

Moon mosaic from 07/13/2020

 

Moon mosaic from 07/26/2020 

 

Jupiter 07/14/2020

 

Saturn 07/14/2020

 

Venus 10/07/2020

 

 

Mars 07/19/2020

 

 

Edited August 4, 2020 by Ken Mitchell

[CraigT82]

41 minutes ago, Ken Mitchell said:

So I recently purchased the Explore Scientific x3 focal extender. Done some tests with it and must say I'm very pleased with its performance.

That's good to hear. Glad you're happy with your choice 👍

[ebdons]

Hi, only decent barlow I have used are the tele-extenders from opticstar (same as meade 5000) i have the 2" x2 and the 1.25' x3 version and find them very good with nice clarity right to the edges, not used a powermate so not sure if these are that inferior? tony.  http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Imagers-Opticstar.asp?p=0_10_5_0_3_66

[Ken Mitchell]

31 minutes ago, CraigT82 said:

That's good to hear. Glad you're happy with your choice 👍

Thank you!

🙏

[johnturley]

38 minutes ago, ebdons said:

Hi, only decent barlow I have used are the tele-extenders from opticstar (same as meade 5000) i have the 2" x2 and the 1.25' x3 version and find them very good with nice clarity right to the edges, not used a powermate so not sure if these are that inferior? tony.  http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Imagers-Opticstar.asp?p=0_10_5_0_3_66

I suspect that they are made by the same company (JOC) as the Explore Scientific ones, their range of 82 degree eyepieces look identical to the ES 82 range.

John

Edited August 4, 2020 by johnturley