Potentially BST starguider issue

[Andy38416]

Hi all,

I was briefly able to use my new BST starguider EP’s last night, but must admit I felt very underwhelmed. I really struggled to position my head to enable me see the entire view through the EP - I’m not sure if this was eye relief or not but I had to press my eye so close I could see my own eyelashes. I’m a non glasses wearer with very good vision.

Ive attached a photo trying to recreated what I could see this morning using a lamppost which is about 250 meters away, this was what I was seeing last night, but the black edge would move around as I tried to move my head into the sweet spot to get rid of it.

any ideas? Am I doing something wrong?

scope is a Nexstar 8SE

 

 

[Daf1983]

Hi there. Did you wind the eyeguard the whole way up? 

[Andy38416]

I must admit I tried various lengths with the eye cup. Maybe it’s just me but I found them a little harder to use.

[Guest]

It's sounds like kidney beaning...

http://stargazerslounge.com/topic/360119-why-is-it-all-black/

Edited August 19, 2020 by Guest

[Andy38416]

Is that normal or does it indicate a fault? I’ve never had it on my plossl EP’s or not that I have noticed.

[Starwatcher2001]

What's the focal length of that particular eyepiece Andy?

[Andy38416]

 

2 hours ago, Starwatcher2001 said:

What's the focal length of that particular eyepiece Andy?

This was with an 8mm EP

Edited August 19, 2020 by Andy38416
I can’t read

[Guest]

3 hours ago, Andy38416 said:

I must admit I tried various lengths with the eye cup. Maybe it’s just me but I found them a little harder to use.

I believe it means that you've not got your eye at the right position.

https://stargazerslounge.com/topic/308112-revelation-32mm-kidney-beaning/?do=findComment&comment=3369617

[Andy38416]

I really struggled to find the sweet spot without seeing the kidney bean somewhere. I’ll try again tomorrow if there’s clear skies as there won’t be any tonight. I just found it really hard to use and spoilt the excitement of new EP’s, I haven’t had to move my head around that much ever before. Steve at FLO replied saying people don’t normally mention kidney beaning on the BST line.
 

hopefully a second night and a bit of patience will help.

[Guest]

I've got the full range of BST StarGuiders and never had an issue with kidney beaning, but I did with the supplied eyepieces of an ancient Meade 4.5" reflector.  That was caused by me looking through the eyepiece either too far away or from the wrong angle, as you have to be square on to the eyepiece.

[Louis D]

I've never seen kidney beaning either with this line of eyepieces.  Since the blackout touches the edge in your image, it's not kidney beaning you're seeing.  Even in extreme kidney beaning, there will always be at least a thin line of visible image near the field stop as you can see in my composite image below:

There is a very slight hint of kidney beaning in the 12mm through 25mm versions as seen above, but it was undetectable visually.  As such, I would imagine the 8mm below would perform similarly.

What you're seeing is probably caused by being too close.  Back off from the eyepiece and approach it slowly until the field stop just pops into view.  That's the distance you should be observing from.  Twist up the eye guard to position your eye at that distance.

[Andy38416]

Thanks Louis, that’s a great reply and really helpful. Never seen that comparison image before either.

hopefully some clear skies tomorrow night but I might try and have a tinker in the day time also to see if I can find the correct zone. I haven’t had a problem for the last couple of years with the 6 or so EP’s I own, maybe it’s the twist up cup messing with me (first time I owned one).

[Andy38416]

2 hours ago, Louis D said:

I've never seen kidney beaning either with this line of eyepieces.  Since the blackout touches the edge in your image, it's not kidney beaning you're seeing.  Even in extreme kidney beaning, there will always be at least a thin line of visible image near the field stop as you can see in my composite image below:

There is a very slight hint of kidney beaning in the 12mm through 25mm versions as seen above, but it was undetectable visually.  As such, I would imagine the 8mm below would perform similarly.

What you're seeing is probably caused by being too close.  Back off from the eyepiece and approach it slowly until the field stop just pops into view.  That's the distance you should be observing from.  Twist up the eye guard to position your eye at that distance.

After watching the linked video below, I think your right Louis.

I guess I’m used to really poor eye-relief from having my eye very close for years to my cheap plossl EP’s, so when I switched out to my new BST’s last night, I kept seeing a constant black shadow like shown in the video at the beginning.

Least I feel a bit happier now and a little bit more educated 😊 I’ll do some daytime viewing and hopefully by night time if there is clear skies will be sorted.
 

[Pixies]

I find that it you raise the eye-cup as far as it goes, then rest the underside of your eyebrow against the eye-cup, it's a good distance.

[Andy38416]

I’m giving it a day time try out as we speak, the 18mm and 15mm seem ok and manageable. The 8mm however I’m struggling with, I just can’t seem to get it where no black area is appearing in the field of view. 
 

naturally it makes me wonder if I should have got the celestron xcel lx EP, but it might just be me struggling. I will keep trying, hoping for clear skies later too.

 

[Pixies]

Ah - I don't have the 8mm. Just the 12 and 18

[John]

Eye cup position is usually the key to avoiding these sorts of issues. I don't wear glasses when I'm observing and find that the uppermost eye cup position is almost always the one that works best.

 

[Andy38416]

I’ve let my wife have a look who knows nothing about telescopes and she said it seemed ok, she said she had to keep her head very very still but she could get the blackness to go away properly.

So it’s just me which I guess is helpful. I’m going to try tonight when everything is a bit calmer and it’s actually dark, I’ve just had the scope pointing up to the sky which is incredibly bright.

i still think it’s more of a getting used to the twist eyecups and better eye relief than anything with the EP itself. Thank you for all the help and comments.

[Don Pensack]

6 hours ago, Andy38416 said:

I’m giving it a day time try out as we speak, the 18mm and 15mm seem ok and manageable. The 8mm however I’m struggling with, I just can’t seem to get it where no black area is appearing in the field of view. 
 

naturally it makes me wonder if I should have got the celestron xcel lx EP, but it might just be me struggling. I will keep trying, hoping for clear skies later too.

 

The Celestron X-Cel LX would have been worse because the eye relief is a bit longer.

I agree that you are simply getting too close to the eyepiece and getting blackouts from being too close to the lens.

The Binoculars example in the video is apropos.

[Franklin]

On 19/08/2020 at 17:36, Louis D said:

I've never seen kidney beaning either with this line of eyepieces.  Since the blackout touches the edge in your image, it's not kidney beaning you're seeing.  Even in extreme kidney beaning, there will always be at least a thin line of visible image near the field stop as you can see in my composite image below:

There is a very slight hint of kidney beaning in the 12mm through 25mm versions as seen above, but it was undetectable visually.  As such, I would imagine the 8mm below would perform similarly.

What you're seeing is probably caused by being too close.  Back off from the eyepiece and approach it slowly until the field stop just pops into view.  That's the distance you should be observing from.  Twist up the eye guard to position your eye at that distance.

 Look at the Pentax XF 12mm. Wow!

[Franklin]

I've a few of the BST Starguiders and I've never had any problems with them. Overall great eyepieces for the cost. Wide field, decent eye-relief and good quality build. Hard to beat for just over £40 a pop.

[Guest]

1 hour ago, Franklin said:

I've a few of the BST Starguiders and I've never had any problems with them. Overall great eyepieces for the cost. Wide field, decent eye-relief and good quality build. Hard to beat for just over £40 a pop.

Same experience here! 👍