#1  
Old 28-07-2021, 08:38 AM
pmrid's Avatar
pmrid (Peter)
Ageing badly.

pmrid is offline
 
Join Date: May 2008
Location: Cloudy, light-polluted Bribie Is.
Posts: 3,341
Imaging with Barlows

You can’t escape Dawes! I guess that’s my main take-away from last night’s session. I wanted to grab some Saturn and Jupiter last night. They were in prime position, the sky was clear and quite cool. All the auguries were good.

Having consulted the specs for my choice of cameras and barlows, I decided to use a EOS 500D with a range of Barlows. And the scope for the night was my BD80.

I have a choice of 4 Barlows. 2 are by Svbony ( a x2 and a x3) but both of those had to be put aside because their barrel is sufficiently smaller that it was pushed out of alignment as soon as the screw of the compression ring is tightened. The tilt is obvious. The barrels are 0.25mm smaller in diameter than those of the GSO (x5) and the Bintel (x2) that were my remaining choices.

For precise focus I used a Bahtinov mask on Archenar to get it just right.

Then the choice of capture software. I began with SmartCap using a routine I found on Cloudy Nights that allowed my EOS to play nicely with SharpCap. My plan was to do Live Stacking. No deal. LiveStack relies on having multiple stars for its alignment routine to work and of course that just isn’t possible with planetary imaging. So I just set up for doing a series of 5000 frame AVI’s but that was a dud with both planets. Despite the care taken with focus, there was just not enough surface detail to work with. Dawes strikes!

The x2 Barlow was no better and image scale that much smaller to boot.

So I turned away from planets and had a run at the 4-day off-full moon. And I just used the x2 Barlow here but although focus was bang-on and the EOS 500D is a 15MP camera, the final images just lacked any crispness at all. They were soft and fuzzy. Not what you want for a moon shot.

So my little play with Barlows was a dud.

Once again, it became clear that if I want clarity and image scale, I’m going to have to move to more aperture and higher focal ratios.

Astronomy is a great source of humility isn’t it?
Reply With Quote
  #2  
Old 28-07-2021, 09:25 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 3,918
Peter,
Even though your equipment was the limiting factor there’s nothing wrong with having a go hey, good on you !!!
How was seeing ?? makes a big difference
I use a 6” and 8” newt with a 600D and Televue Powermates for planetary ( only dabble in it , nothing too serious )
On stable nights of good seeing I manage to process some half respectable images for the level of equipment I use ( beginner stuff )
My focal ratio for imaging Saturn and Jupiter is usually f21 to f30 ( 4 x Powermate and 5 x Powermate)
If you don’t want to spend too much money on a planetary scope, you can pick up a 6” newt for $400 and get some half decent images with your 500D and Barlow’s or Powermates
Here’s some of my images from last winter with my 6” newt and 600D, beginner stuff but I’m happy and have fun dabbling in planetary. I’m mainly a DSO imager
Thanks for your post
Cheers
Martin
Attached Thumbnails
Click for full-size image (950F5156-DCB9-45B2-A682-E9AA6C895A8C.jpg)
64.0 KB34 views
Click for full-size image (5140E343-95E5-432E-8849-275D193A8452.jpeg)
51.0 KB45 views
Click for full-size image (7B0482F1-2A74-49B7-B584-A62F3D3470A4.jpeg)
37.7 KB47 views
Reply With Quote
  #3  
Old 28-07-2021, 11:46 AM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 8,430
As Martin says, the seeing is important.
I'd also add, using a suitable camera. The current Cmos cameras can run at high frame rates effectively "freezing" the seeing and providing those "lucky imaging" moments.
I use barlows/ powermates all the time for my solar imaging with the ASI 1600 camera, working around f16.
Reply With Quote
  #4  
Old 02-08-2021, 02:39 PM
pmrid's Avatar
pmrid (Peter)
Ageing badly.

pmrid is offline
 
Join Date: May 2008
Location: Cloudy, light-polluted Bribie Is.
Posts: 3,341
I have retried this with an RC8 (200mm f8) and an ASI290MC. Jupiter and Saturn were in good position so I also threw in a Bintel x2 Barlow for good measure and got up to f16. Skies were clear but seeing was lousy - very high humidity and lots of instability. So the results were lousy.

I have since picked up a cheap GSO 8 inch f5 newt with a bung focuser. That’s my current project.

However, I must say I have not found the Barlows I have been using achieved anything like decent results. I have never had a Power,ate so I can’tbcompare. Are they really worthwhile?

Peter.
Reply With Quote
  #5  
Old 02-08-2021, 06:27 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 8,430
Peter,,
If the seeing allows you to get good results with the Barlow, then the Powermate has the ability to give you excellent results.
Reply With Quote
  #6  
Old 03-08-2021, 08:05 PM
Camelopardalis's Avatar
Camelopardalis (Dunk)
Drifting from the pole

Camelopardalis is offline
 
Join Date: Feb 2013
Location: Brisbane
Posts: 5,243
Peter, living so close to the water can make the seeing extra variable. No forecast that I’ve found leads to predictions any better than flipping a coin.

The one important thing to do is to get out there and take a look regularly. The more you look, the more experience you will get in recognising good seeing from bad. There’s really no simple shortcut. Start with an eyepiece over a few nights and see how you go, but also bear in mind the seeing can vary over the course of an evening.

Also watch out for any local thermals, such as a neighbour’s air conditioning unit spewing out hot air.

FWIW, I’ve had some luck in the past with my C11 + Powermate, but the nights it really makes a difference are few and far between.
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 01:15 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Advertisement
Limpet Controller
Advertisement
Testar
Advertisement
Bintel
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement