Another BST StarGuider EP On It's Way...

[John]

Well manufacturers specs are often a little wide of the mark.

 

 

[Guest]

6 hours ago, BLUEThumb said:

Adoo Merlin

I have just bought  A StarGuider 1.25 8mm  yesterday, can't wait for its arrival' have read a bit about these eyepeices and they appear to have good reviews,i was going to buy the 5mm one ,but in the  end opted for the 8mm,as it  has a 60 degree fov  (I THINK), appologies if i am wrong.

I've got the 8mm one and I'm happy with it. 

[Guest]

1 hour ago, John said:

Well manufacturers specs are often a little wide of the mark.

 

 

Perhaps the 5mm will work out nearer the 6mm you recommended then?🤣

[Louis D]

25 minutes ago, merlin100 said:

Perhaps the 5mm will work out nearer the 6mm you recommended then?🤣

Here's the 5mm Paradigm/BST up against some other high power eyepieces.  It seems to be pretty close to the quoted focal length based on its neighbors' magnifications.

I've yet to find a single eyepiece egregiously far off as far as focal length goes.  Usually, eye relief and AFOV are commonly exaggerated.  Alternatively, the 6.5mm HD-60 should play up the fact it has a 65 degree AFOV like a Pentax XL as seen in the last image.

[Guest]

Just arrived from Auntie FLO, this morning. 😊

[Louis D]

As that is the only BST focal length I don't have, I'm quite interested in hearing your thoughts on it.

Clear skies!

[Guest]

I had a quick look through the 8mm and 3.2mm on Venus this evening.  The phase was quite distinct, but I don't think seeing conditions were at their best, due to a slight haze in the sky.  The moon was a low crescent, dipping below the roof lines before I could get a ganders at it.  I think I'll have to wait till it's more prominent...

Just for the hell of it, I tried them on Arcturus.  It was bright enough, but again, I couldn't get a sharp image because of the haze.  As I already knew they would, the celestial bodies move very fast at high magnification!

[Louis D]

16 hours ago, merlin100 said:

I had a quick look through the 8mm and 3.2mm on Venus this evening.  The phase was quite distinct, but I don't think seeing conditions were at their best, due to a slight haze in the sky.  The moon was a low crescent, dipping below the roof lines before I could get a ganders at it.  I think I'll have to wait till it's more prominent...

Just for the hell of it, I tried them on Arcturus.  It was bright enough, but again, I couldn't get a sharp image because of the haze.  As I already knew they would, the celestial bodies move very fast at high magnification!

If you get a clear night, let stars of different magnitudes drift to the edge and note if they change shape indicating edge aberrations.  Also, try refocusing a star at or near the edge to see if that improves its sharpness.  Racking a star near the edge inside and outside of best focus can easily reveal if the eyepiece has edge astigmatism because the star will stretch radially on one side and tangentially on the other.  If it is minor, it will appear nearly pinpoint at best focus.  If it's bad, it will appear spiky at best focus.  If you keep objects centered with a driven mount, edge astigmatism does not matter very much, but if you use an undriven mount, especially at high powers, you really want edge to edge sharpness to extend "dwell" time to observe an object before nudging the scope again.

Edited April 26, 2020 by Louis D

[rwilkey]

On 22/04/2020 at 17:49, merlin100 said:

I can see it being used for lunar observing, when conditions permit.  

Hi Merlin, I found the 3.2mm perfect for Lunar viewing, but not so good for anything else.  I am sure you will like it.  Clear skies!

[Guest]

1 hour ago, rwilkey said:

Hi Merlin, I found the 3.2mm perfect for Lunar viewing, but not so good for anything else.  I am sure you will like it.  Clear skies!

That's my main subject of interest with this eyepiece.😉

[Guest]

I had a ganders at the moon and Venus this evening. The phase of Venus was very apparent using both the 8mm and 3.2mm EP's.  Although Venus was a bit darker in the 3.2mm EP, it was still bright. 

On the moon, both the 8mm and 3.2mm EP's weren't that clear. I used a 10mm EP (OEM) and I could also see the scintillation through that too.  The atmosphere wasn't quite good enough for higher power observing. Lastly, I checked it with the supplied 25mm EP and the scintillation was far less obvious. 

[Louis D]

15 minutes ago, merlin100 said:

I had a ganders at the moon and Venus this evening. The phase of Venus was very apparent using both the 8mm and 3.2mm EP's.  Although Venus was a bit darker in the 3.2mm EP, it was still bright. 

On the moon, both the 8mm and 3.2mm EP's weren't that clear. I used a 10mm EP (OEM) and I could also see the scintillation through that too.  The atmosphere wasn't quite good enough for higher power observing. Lastly, I checked it with the supplied 25mm EP and the scintillation was far less obvious. 

Center a bright star (Venus might even work) and defocus it pretty far.  You should be able to see the atmospheric (or telescope tube) turbulence as bubbling in the defocused image.  You can sort of judge the quality of the seeing in this manner.

Stick your hand in front of the objective/end of tube to see more cool thermal effects.  It reminds of the view through a thermal imager.

[Guest]

1 hour ago, Louis D said:

Center a bright star (Venus might even work) and defocus it pretty far.  You should be able to see the atmospheric (or telescope tube) turbulence as bubbling in the defocused image.  You can sort of judge the quality of the seeing in this manner.

Stick your hand in front of the objective/end of tube to see more cool thermal effects.  It reminds of the view through a thermal imager.

I was getting the thermal currents from my hand for sometime...  I could see no sign of astigmatism, but I don't feel experienced enough to be 100% sure.  I tried to separate the Izar double, but with no joy.  There did seem to be slightly better viewing conditions this evening.  The 8mm and 3.2mm aren't parfocal, from what I can tell, as you need to readjust the focusing after changing EP's.