17 replies to this topic

[rjlastroscanvt]

I have the above mentioned 3mm  Delite for my 4" refractor (Stellarvue  SVX 102D) as sort of my maximum magnification.

I can't for the life of me get any consistent image through it, nor can I determine how to utilize the sliding/expanding insertion section of the eyepiece which I assume is to help with back focus?

What is it I am missing?

Edited by rjlastroscanvt, 16 June 2025 - 11:39 AM.

[T1R2]

It should be fine, I think you are seeing the effects of turbulence that causes the image to blur and look like heat coming off the road or looking through water, so wait til the jet stream is away from you or view in the opposite direction of it. ....Though you are over the theoretical max a by 36x not too far over, but the max I'd would use.  I would want about (204x- 220x for my normal planetary/ double star power power but its useful on the moon and doubles and Saturn should be really nice in it later on over the yrs. to come when the rings star opening out, Jupietr Im not so sure will yield great views at that mag depending on the softness of its contrast to this time period but could improve and still give very nice views if its color darkens. .

 

Someone else will have to tell you how to use the eyecup or you could call TV, but basically you adjust it so you can comfortably see the field stop at the edges without getting too close to the eye lens and getting inside the optimum eye relief or exit pupil stop where you tend to get blackouts when your eye too close to the eye lens. 

Edited by T1R2, 16 June 2025 - 01:04 PM.

[SeattleScott]

Sliding/expanding insertion section? Are you putting the eyepiece in upside down?

I will let those with the eyepiece chime in, but the sliding portion is supposed to be an adjustable height eyecup, not something to be inserted into the telescope. Generally, if you wear glasses, it tends to stay down, and if you don’t, you probably want to raise it.

[richardr]

Your Telescope is f/7 which means that its focal length would be 714mm.  magnification is equal to 3mm/714mm which is 238x.  This is only likely to work on the Moon, as it is the only object bright enough to handle that magnification in a 4" scope.  You will need a superb mount at that power to see anything in a 4" scope.  

[SoCalPaul]

When you say, you can't get a consistent image, please explain. Are the images sometimes sharp, sometimes not? Does this fuzziness come and go in waves? Or is it good one night, then not the next? Something entirely different?

 

My immediate thought is that you could be experiencing the effects of poor "seeing," i.e. unsteady air above your scope that blurs the image in waves. At 238x, you're using significant magnification, although that scope should be able to deliver crisp images at that scale, if the seeing is good.

 

It could also be that your scope needs more cooldown time.

 

With regard to that sliding portion, I believe that is purely for your own visual comfort, to put the rubber eyeguard at a distance from the eye lens so that you can see the entire field of view, but not so close that you get kidney-bean effect or your eyelashes bump into it, etc.

 

Clear skies,

Paul

[havasman]

It's probably simply that your conditions will not often support those magnifications/exit pupils/ focal lengths. Wishing doesn't make it true and it's always advised to ease your way down to your "maximum magnification" so you do not overshoot it by relying on some chart, advertisement or video instead of your own experience.

 

The twist-up eye cup is to adapt the long eye relief of that ep to your preference. Read the Delite instructions included in the box or on the TV website. It is covered.

[rjlastroscanvt]

Thank you all who answered.

I suspect that what havasman said is probably the case.

Though theoretically on the Televue website graphing for my setup and that eyepiece (and in part why I felt I could use/buy that eye piece).

I think it's more likely that a good quality 4mm or perhaps a Pentax 3.5mmXW will give a wider range of practical application with almost as much magnification.

[Starman1]

Thank you all who answered.

I suspect that what havasman said is probably the case.

Though theoretically on the Televue website graphing for my setup and that eyepiece (and in part why I felt I could use/buy that eye piece).

I think it's more likely that a good quality 4mm or perhaps a Pentax 3.5mmXW will give a wider range of practical application with almost as much magnification.

I have an excellent 4" f/7 triplet refractor, but found magnifications over 200x were not clear because of my eye--floaters inside, corneal issues on the outside.

Even if the 3mm eyepiece focused just fine.

193x (3.7mm eyepiece) works far better.

Your last line is probably correct.

[mountain monk]

I have the 4mm but it is rare that I can use it because of poor seeing. The 3mm would be rarely, rarely used in my conditions.

 

Dark, clear, calm skies.

 

Jack

[CrazyPanda]

I have the above mentioned 3mm  Delite for my 4" refractor (Stellarvue  SVX 102D) as sort of my maximum magnification.

I can't for the life of me get any consistent image through it, nor can I determine how to utilize the sliding/expanding insertion section of the eyepiece which I assume is to help with back focus?

What is it I am missing?

The "sliding" section is the adjustable eye guard. It is intended to make it so you can customize the effective eye relief of the eyepiece to your liking. It doesn't have anything to do with back focus.

 

Here is how you use it:

 

https://www.youtube....h?v=gn2sS8OXr9w

 

Twist the two rubber knurled rings opposite one another to loosen, slide the guard to your liking, re-tighten the rings to lock them in place.

Edited by CrazyPanda, 18 June 2025 - 05:27 AM.

[Megawatt]

If you are not familiar with long eye relief eyepieces like the DeLite, you might be having issues with eye placement. That is what the sliding section is for. Having the eyecup set too low will cause misalignment of the exit pupil and the image will suddenly black out. It is crucial to understand how to set the eyecup in any eyepiece with 20mm of eye relief, especially at such short focal lengths. 

 

To set the eyecup position, start with it all the way up, and gradually lower it until you can just see the edge of the field. Then tighten the eye guard so it doesn't slide around. 

 

I use a 3mm Radian, which is similar to the DeLite, with my 3-inch f/6 refractor to achieve maximum magnification and I have no issues. I have even used it with a 2x barlow for double star observing. 

[Oldfracguy]

I have the above mentioned 3mm  Delite for my 4" refractor (Stellarvue  SVX 102D) as sort of my maximum magnification.

I can't for the life of me get any consistent image through it, nor can I determine how to utilize the sliding/expanding insertion section of the eyepiece which I assume is to help with back focus?

What is it I am missing?

I use a 3mm DeLite in 4" f/7 scopes when the seeing permits quite a bit.  That scope you have is capable of high magnifcation, and if I may say so, it deserves a 3mm DeLite.  

 

There is a ring below the upper eyepiece portion that rotates so you can loosen that upper portion and slide it upward to get the optimum eye placement for your tastes:

 

 

 

Loosen that ring, slide the upper portion up or down to where you want it, then retighten that ring.  Also, when you pull off the small bottom plastic end cap cover, only hold onto the bottom portion of the barrel or else you might accidentally pull the upper portion up away from where you had set it.  I'm speaking from experience here  .

Edited by Oldfracguy, 18 June 2025 - 09:43 PM.

[Jehujones]

I use a 3mm DeLite in 4" f/7 scopes when the seeing permits quite a bit.  That scope you have is capable of high magnifcation, and if I may say so, it deserves a 3mm DeLite.  

 

There is a ring below the upper eyepiece portion that rotates so you can loosen that upper portion and slide it upward to get the optimum eye placement for your tastes:

 

101_3303_2.JPG

 

 

Loosen that ring, slide the upper portion up or down to where you want it, then retighten that ring.  Also, when you pull off the small bottom plastic end cap cover, only hold onto the bottom portion of the barrel or else you might accidentally pull the upper portion up away from where you had set it.  I'm speaking from experience here  .

No worries, they’re easy to adjust. I collapse mine when I put them away. I store them vertically.

 

 

[Shorty Barlow]

 

I'm partially paralysed in my right hand, so I also find adjusting the eyecups on my DeLites (I have four of them) a tad difficult. It's the locking ring that seems to defeat me.

 

 

I get 238x with my f/7 102mm Altair Starwave which is around a 0.42mm exit pupil. These days/nights I'm more likely to use a 3-6mm TV zoom. 238x is do-able on the Starwave, particularly for Mars, although it is pushing it a little on a four inch scope even with really good glass. 

 

 

At 238x I usually need my Vixen HAL-130 tripod with half pillar to get a consistent stability. 

 

 

Which is why the zoom is so useful. I can easily drop the magnification until I need it.

[Jehujones]

That’s understandable 

[Shorty Barlow]

I use a 3mm DeLite in 4" f/7 scopes when the seeing permits quite a bit.  That scope you have is capable of high magnifcation, and if I may say so, it deserves a 3mm DeLite.  

 

There is a ring below the upper eyepiece portion that rotates so you can loosen that upper portion and slide it upward to get the optimum eye placement for your tastes:

 

101_3303_2.JPG

 

 

Loosen that ring, slide the upper portion up or down to where you want it, then retighten that ring.  Also, when you pull off the small bottom plastic end cap cover, only hold onto the bottom portion of the barrel or else you might accidentally pull the upper portion up away from where you had set it.  I'm speaking from experience here  .

I think the TV end caps are a tad tight (especially in the cold) & can enable the distance setting to alter if you pull too hard. I use looser generic end caps now. 

[Shorty Barlow]

That’s understandable 

I kinda miss that DeLite flat 62 degree field with the zoom though.

[RichA]

I have an excellent 4" f/7 triplet refractor, but found magnifications over 200x were not clear because of my eye--floaters inside, corneal issues on the outside.

Even if the 3mm eyepiece focused just fine.

193x (3.7mm eyepiece) works far better.

Your last line is probably correct.

Variability of seeing conditions, height of object over the horizon, avoidance of heated rooftops, asphalt, etc.  300x power or so won't kill a 4 inch apo.  It's nearing a kind of limit, but hardly dire. A good power for double stars, going deep on globular clusters and nebulas like orion that have intricate detail that shows up at higher powers and kind of expanding the 3D look of relief on the moon.