Possible Barlow issues

[loakessg]

Good morning

I seem to have focusing problems when using my 5mm - BST Explorer ED Eyepiece with my skywatcher 2x Barlow. Using the eye piece alone I get a pretty sharp image but when used with Barlow the focus seems reduced. Is there some incompatibility with these items or am I just going blind in my old age. I believe I'm not over stretching the ability of my scope, or perhaps I am.

Thoughts?

Thanks

Sean

[brantuk]

Hi Sean - I used to have your set up and it was rare I could push it up much over 200x magnification just due to average seeing conditions. With a focal length of 750mm and an effective eyepiece size of 2.5mm your mag is 300x. Not unreasonable on a very clear, transparent, dry night with top quality eyepieces and good seeing. But at f-5 in current seeing all you end up magnifying is the imperfections in the atmosphere. I think your view will go very grainy and faint. Best hold off on high mag until the weather is more accommodating is what I'd suggest. Hth

(Also checking the specs - 300x is the max useful mag for your scope just fyi)

[loakessg]

5 hours ago, brantuk said:

Hi Sean - I used to have your set up and it was rare I could push it up much over 200x magnification just due to average seeing conditions. With a focal length of 750mm and an effective eyepiece size of 2.5mm your mag is 300x. Not unreasonable on a very clear, transparent, dry night with top quality eyepieces and good seeing. But at f-5 in current seeing all you end up magnifying is the imperfections in the atmosphere. I think your view will go very grainy and faint. Best hold off on high mag until the weather is more accommodating is what I'd suggest. Hth

(Also checking the specs - 300x is the max useful mag for your scope just fyi)

Hi.. thanks for the reply. I do have pretty good seeing conditions here (well not much light polution but guess the atmospheric conditions could be better at the moment) but do understand what you are saying.. looks like time to invest in a new eyepiece with less magnification.

Sean

 

[Putaendo Patrick]

I think Brantuk has probably hit the nail on the head, but you might want to check your Barlow with the 10mm and 25mm EPs you have. This should reveal whether the Barlow has any inherent problems.

A recent discovery for me are the Astronomical Seeing tables at https://www.meteoblue.com

These show a number of factors which may affect the seeing at your location.

[Mak the Night]

I don't know what type of Barlow you are using. Sky-Watcher tend to supply two varieties included with their scopes. One of them is fairly cheaply constructed predominantly out of plastic. I honestly can't say anything good about these Barlows and they are very difficult to bring into focus with anything I have found.

Some Sky-Watcher scopes are equipped with the Sky-Watcher Deluxe 2x Barlow (Synta-made). This is quite a decent quality Barlow and I find higher quality than the Celestron Omni (GSO-made) Barlows. I have the Celestron equivalent of the 'Deluxe' (below) which was originally from the Celestron AstroMaster Kit. FLO sell it as the 'Celestron 2x Universal 1.25" Barlow'.

It is definitely worth £23. I often recommend it. Mine still goes out with my EP case even though I have other Barlows. I find the unthreadable/detachable Barlow element useful.

http://www.firstlightoptics.com/celestron-eyepieces/celestron-2x-universal-125-barlow.html

[loakessg]

24 minutes ago, Mak the Night said:

I don't know what type of Barlow you are using. Sky-Watcher tend to supply two varieties included with their scopes. One of them is fairly cheaply constructed predominantly out of plastic. I honestly can't say anything good about these Barlows and they are very difficult to bring into focus with anything I have found.

Some Sky-Watcher scopes are equipped with the Sky-Watcher Deluxe 2x Barlow (Synta-made). This is quite a decent quality Barlow and I find higher quality than the Celestron Omni (GSO-made) Barlows. I have the Celestron equivalent of the 'Deluxe' (below) which was originally from the Celestron AstroMaster Kit. FLO sell it as the 'Celestron 2x Universal 1.25" Barlow'.

It is definitely worth £23. I often recommend it. Mine still goes out with my EP case even though I have other Barlows. I find the unthreadable/detachable Barlow element useful.

http://www.firstlightoptics.com/celestron-eyepieces/celestron-2x-universal-125-barlow.html

I have the "Deluxe" version   I think I need to do what the other guys have suggested ie wait for better conditions and or try smaller eyepieces to check the barlow before i splash out on a new barlow. Roll on decent skies.

Thanks

[Mak the Night]

3 minutes ago, loakessg said:

I have the "Deluxe" version   I think I need to do what the other guys have suggested ie wait for better conditions and or try smaller eyepieces to check the barlow before i splash out on a new barlow. Roll on decent skies.

Thanks

It is probably the seeing and overall atmospheric conditions probably then. A 6" aperture should resolve well to around 250 - 300x for targets like the Moon though. The weather, conditions, position of target and even the time (dawn/dusk/night) can all help or hinder particular targets. Some of the best views of Jupiter and Venus I've had have been when they are setting or rising in twilight. I viewed the Moon rising a few nights ago low in the east (around azimuth 314° SE, altitude 7.1° to 318°SE, 9.2°) with a faint haze but got some superb Terminator shadow detail with a 90mm Mak at 100x. I managed around 140x with a Barlow but the views at 100x were sharper. Sometimes I've pushed the 90mm to 166.6x. For a three and a half inch scope that's near its theoretical resolution limit. A lot depends on conditions. At around 10° altitude you are looking through a lot of atmosphere.

[REG78]

I found tht myself using the plastic 1 supplied with my skywatcher th 10mm EP is nice n clear wen I attach th Barlow Jupiter is just a fuzzy disc with no detail at all so stopd using th Barlow I just ordered th GSO Barlow has it got detachable element on it never said on th read up about it 

[Mak the Night]

Just now, REG78 said:

I found tht myself using the plastic 1 supplied with my skywatcher th 10mm EP is nice n clear wen I attach th Barlow Jupiter is just a fuzzy disc with no detail at all so stopd using th Barlow I just ordered th GSO Barlow has it got detachable element on it never said on th read up about it 

Which GSO Barlow? I have a TS Optics 2.5x apochromatic Barlow that was manufactured by GSO. It doesn't have a detachable element.

 

[REG78]

I orderd it of 365astronomy was about £22 it says GSO on th top of th Barlow 

[REG78]

This is th 1 I orderd

[Mak the Night]

41 minutes ago, REG78 said:

This is th 1 I orderd

Oh right, I've seen these. It's very possibly the same as this TS Optics Barlow: http://www.teleskop-express.de/shop/product_info.php/info/p53_TS-TSB21-Barlow-Linse-1-25-Zoll---1-5fach-und-2fach---visuelle-und-fotografische-N.html

I know TS Optics have a lot of their stuff made by GSO (I'm pretty sure they're basically re-badged).

There's a good possibility that yours has a removable element.

[REG78]

Nice 1 cheers for th info mak

[Mak the Night]

You're welcome.