Jump to content

sgl_imaging_challenge_2021_annual.thumb.jpg.3fc34f695a81b16210333189a3162ac7.jpg

Talx2 barlow


Recommended Posts

Was out last night and had a braw time. Was with a few freinds and 3 scopes in total. My problem was that when I used my tal barlow on my 127mak with my 18mm bst, I noticed a distinct drop in visual quality. Venus was ok and moon was stunning with earthshine but when I looked at jupiter it was below average for my usual veiwing experience. Definition was lost. Was the same for saturn which was a real shame as it was my 1st time viewing the ringed one. I could just make out a gas band and I'm sure 1 moon as well. I know both of these planets were low on horizon and atmosphere is thicker and makes viewing worse but should it degrade so much?

I dont think at a balowed equivilent of 9mm that that should be too powerfull for my scope (127x1500).

Also when my freind used the balrow in his meade 70etx with his 9mm ep, it was stunning.

Any ideas whats going on?

Link to comment
Share on other sites

If I'm not mistaken the ETX 70 has a much shorter focal length. 350mm? If this is the case then you would have only been viewing at around 78x even with the barlow.

With the 127Mak you would have been viewing at about 333x with the 9mm and barlow which is pushing the 5" mak too far under UK skies. The 9mm without the barlow is about the limit most of the time, but even that will vary with atmospheric.

Link to comment
Share on other sites

Thanks for reply Baz.

The 127 was only the barlow and 18mm bst to make the equivilent of a 9mm. I never used the 9mm with the barlow in the mak. I knew the limit for the mak is 8 or 9 mm but I was getting realy good views of venus and orion neb with the barlowed 18 which was why I couldnt understand the poor performance on jupiter and saturn.

Link to comment
Share on other sites

Yep, your right. I didn't read your post right. Apologies!

You were still viewing at a much higher mag than the Meade though.

166x compared to 38x. That will magnify the atmospheric disturbances as well, so it could still be down to too much mag for the conditions. You could wait for Saturn to rise higher so you will be viewing through less of it.

Don't forget the cool down time that te Mak needs too. I find that mine needs between half and three quarters of an hour to cool down and it makes a dramatic difference to the quality of the view.

Link to comment
Share on other sites

I have a 127 mak and just a standard 2xbarlow. Last night I tried using a 8mm bst ep plus the barlow on Mars and Saturn and found it to be too high a magnification. So I changed to a 12mm celestron excel lx, smaller image of course but crisper image. Saturn was still very low down amongst the lp but could still see some very faint banding and one moon. On Mars there was some faint markings and ice cap. I looked at Jupiter with my Tal1 refector with similar results, low mag crisp image, high mag fuzzy image. Its a trade off. Even on the moon last night as soon as you up the mag too high you get a blurry image, like looking through water.

Link to comment
Share on other sites

Seeing has been terrible the last few nights, especially low down in the soup, where both jupiter and saturn are unless you're out at silly o'clock. Larger apertures are more susceptible to effects of seeing, especially when viewing at higher powers.

Could also just be an issue of cooling. Those maks take AGES to cool properly.

I have a Tal 2x and have had no issue with it whatsoever.

Link to comment
Share on other sites

Baz,

I have effectively the same scope + a Tal 2x barlow and a BST 15tmm which I've used before in combination quite effectively on bright targets.

So I suspect it's down to bad seeing (instability in the atmosphere as I understand it) in combination with targets which are too low in the sky.

If you're out tonight maybe try out that combination on Mars which is higher in the sky or when the moon when it is higher in the sky. I don't think the seeing conditions are going to be much different to yesterday though at least where I am.

I was using a 7mm EP on Mars last night at about 10pm and seeing some quite good detail (well about as good as I've seen it before anyway). But I tried the same combination on the moon half an hour earlier and it was awful compared to previous nights, I looking through too much atmosphere.

Best of luck

Tyr

Link to comment
Share on other sites

Cheers for replies.

I rekon it must just have been atmospheric conditions that affected my viewing. I had been out for over an hour before trying for Jupiter and 2 hours for Saturn so the scope should have cooled sufficiently by then. Don't get me wrong it was delivering excellent views of everything else we looked at and once again was better visually than both the other scopes.

In time I'm hoping to have enough ep's so that I don't need a Barlow but that will take time.

Link to comment
Share on other sites

Went out this evening from 10pm - 12am, and had fantastic time.

Got Mars at 250x clear as a bell with markings on planet and Ice cap just visible.

Did some Bino Viewing whilst waiting for Saturn to rise. Even whilst low in the sky I managed some good viewing but boy when it rose to a nice height just before midnight I managed excellent focus with my 6mm TMB clone. I even managed to clearly see banding in the ring system.

I then tried the 10mm SW plossl barlowed to 5mm. I managed reasonable focus but lost clarity and could no longer make out the banding on the rings.

I tried my 16.8mm ortho barlowed to 8.4mm and got a nice crisp image and though a much smaller image could just make out banding in the rings.

So all in all a good evenings viewing.

Link to comment
Share on other sites

.

Got Mars at 250x clear as a bell with markings on planet and Ice cap just visible.

Yeah ok I'm jealous :(

Sounds like it was a braw night. I had the oportunity to go out last night but decided against it as I have a 30 mile bike run planned for today and thought I better have an early night. Never happened thanks to new series of wheeler dealers starting just as I was going to turn the telly off. (was on +1).

No matter, shall hopefully pop out for a bit tonight if it stays clear.

I'm glad to see the scope can take a high power ep as I am looking to order my 1 a month ep and not sure what to get but thinking maybe a 15mm with a look to barlow to 7.5 if this will work. Or maybe a 24 for more of a wide view and try for galaxies.

Any suggestions?

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.