17 replies to this topic

[lunarmonday]

Hey everyone!

 

Got a SW Evolux 62ed that has been great for astro. Wife finally wanted a viewing session with an eyepiece. She's generally a fan of the planets and moon over DSO. 

 

I bought a Baader Hyperion (1.25 & 2mm dual) 5mm as based on all the calculations it is well within the ability of the scope. 

Scope is 400mm focal length and 62mm aperture. 80x seemed to be conservative based on everything I read and close to a conservative limit but still below ( I assumed 35x for every inch in order to not overdo it)

 

My issue is tonight when trying to view the moon, the piece was completely out of focus. No matter what I tried with moving the piece further away from the barrel, tilting it etc. I had no luck. I double checked with my DSLR and everything focused fine. Scope had time to acclimate to temperature and seeing was good. 

 

Does the eyepiece need to be further back a la back focus? I had assumed just inserting it to the 2" level would make it good to go. 

 

Thank you all for any insights!

[eblanken]

Take a tip from Cloudy Nights (CN) member TOMDEY and do this experiment to find the focal plane in your scope . . .

 

Ed

 

P.S. Welcome to CN . . . 

Attached Thumbnails

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Edited by eblanken, 07 June 2025 - 12:32 AM.

[eblanken]

Also read this thread . . . .

 

https://www.cloudyni...91-not-focusing

 

Best,

 

Ed

[Jon Isaacs]

Hey everyone!

 

Got a SW Evolux 62ed that has been great for astro. Wife finally wanted a viewing session with an eyepiece. She's generally a fan of the planets and moon over DSO. 

 

I bought a Baader Hyperion (1.25 & 2mm dual) 5mm as based on all the calculations it is well within the ability of the scope. 

Scope is 400mm focal length and 62mm aperture. 80x seemed to be conservative based on everything I read and close to a conservative limit but still below ( I assumed 35x for every inch in order to not overdo it)

 

My issue is tonight when trying to view the moon, the piece was completely out of focus. No matter what I tried with moving the piece further away from the barrel, tilting it etc. I had no luck. I double checked with my DSLR and everything focused fine. Scope had time to acclimate to temperature and seeing was good. 

 

Does the eyepiece need to be further back a la back focus? I had assumed just inserting it to the 2" level would make it good to go. 

 

Thank you all for any insights!

 

Are you using a diagonal?   For photography, one generally does not use a diagonal but for visual, it's necessary.

 

Jon

[Dave Mitsky]

Are you using a diagonal?   For photography, one generally does not use a diagonal but for visual, it's necessary.

 

Jon

I had the same thought, Jon. 

[lunarmonday]

 

Are you using a diagonal? For photography, one generally does not use a diagonal but for visual, it's necessary.

Jon

 

Is it functionally necessary or just practically? I've viewed without a diagonal before so I'm confused. 

[PKDfan]

Is it functionally necessary or just practically? I've viewed without a diagonal before so I'm confused.

Hi lunarmonday !

I have the 62Evolux and use 2" diagonals and i have zero issues with bringing any of my eyepieces to focus so if your working without one then you will need to add the same diagonal length into the equation.

About 110-115 millimeters is the normal length of a diagonal so without that there you must use an extension tube of sufficient length ie 115mm to get the same working difference.

And it depends where the focal plane of the eyepiece is too.

Fortunately they are cheap to buy.

A 2inch extension might be enough.

Conditions are horrid here now or i'd test it without using a diag as i have a 2inch extension tube.

PM if you've got any followup questions.


Lance
CSS

[lunarmonday]

Hi lunarmonday !

I have the 62Evolux and use 2" diagonals and i have zero issues with bringing any of my eyepieces to focus so if your working without one then you will need to add the same diagonal length into the equation.

About 110-115 millimeters is the normal length of a diagonal so without that there you must use an extension tube of sufficient length ie 115mm to get the same working difference.

And it depends where the focal plane of the eyepiece is too.

Fortunately they are cheap to buy.

A 2inch extension might be enough.

Conditions are horrid here now or i'd test it without using a diag as i have a 2inch extension tube.

PM if you've got any followup questions.


Lance
CSS

Thank you for that info! I did the lightbulb/paper test and it does look like the eyepiece is a few inches too close.

Would getting a 1.25 diagonal matter? It’ll push my eyepiece back another 24mm but that’s all my local shop has (I’d like to support them as much as possible)

[lunarmonday]

Also read this thread . . . .

 

https://www.cloudyni...91-not-focusing

 

Best,

 

Ed

 

 

Take a tip from Cloudy Nights (CN) member TOMDEY and do this experiment to find the focal plane in your scope . . .

 

Ed

 

P.S. Welcome to CN . . . 

Thank you for both of those! Couldn't get the tape test to work but it directed me to the paper/lightbulb test. 

[PKDfan]

Thank you for that info! I did the lightbulb/paper test and it does look like the eyepiece is a few inches too close.
Would getting a 1.25 diagonal matter? It’ll push my eyepiece back another 24mm but that’s all my local shop has (I’d like to support them as much as possible)

It'll probably work. I've got a Celestron 1 1/4" prism that i've hardly used but it does work, but i haven't thoroughly explored how each eyepiece works with it in the little apo.

Conditions are horrible right now or else i'd test it for you.

As for power limits, a 5mm eyepiece has my Evolux barely breathing hard. I actually go out with only two things if Lunar observing is on and thats a 4.5Morpheus and a 2X Barlow for 167X and nothing amiss is notable except for incredible details so don't sweat a mere 80X.

I even enjoy the stock UWA 5mm Planetary2 that shipped with my Evostar 100mm for 80X.

Brightness is just fine at a Barlowed 167X.


And Good on you for supporting our local astrostore !



Lance
CSS

[ABQJeff]

Thank you for that info! I did the lightbulb/paper test and it does look like the eyepiece is a few inches too close.
Would getting a 1.25 diagonal matter? It’ll push my eyepiece back another 24mm but that’s all my local shop has (I’d like to support them as much as possible)

Most 1.25” diagonals add more than just 24mm to light path, but if that is the case and you are several inches short even with focuser racked all the way out that won’t do on its own. You will need to add an extension, filter wheel, 2” diagonal, etc. to get your optical path longer.

Take relief in your situation though, your issue is much easier to solve than the opposite: too little backfocus. That requires foregoing 2” eyepieces, filter wheels or eveb having to cut the refractor tube.

Backfocus is the top reason I find refractors to be the most difficult telescope design to use (contrary to general consensus.)

[Jon Isaacs]

1.25 inch diagonals typically add about 75 mm = 3 inches to the light path.

 

Jon

[eblanken]

Hi again,

 

Lance (in posts #7 & 10) gives good input as he has the same scope. Jon is right: 1.25 inch diagonal adds 75mm or so and 2 inch diagonal adds 100mm or more and a straight thru extension is whatever it is adding . . . The key is to understand where the focal plane is located at for an object at infinity and please know that a closer object moves its focus out some more also . . .

 

Best,

 

Ed

Edited by eblanken, 07 June 2025 - 06:17 PM.

[PKDfan]

Hi again,

Snipped . . . The key is to understand where the focal plane is located at for an object at infinity and please know that a closer object moves its focus out some more also . . .

Best,

Ed

Thats an excellent point Ed ...both object distance for terrestrial and the focal plane location of the eyepiece really matter.

I can't recall the eyepieces but they're can be at wildly different places in the tubes travel but so far so good all work.

Many of mine are hybrids with both 2" and 1 1/4" fit which helps with changing over from large true fields of the big glass to lunar and planetary powers.



CSS
Lance

[lunarmonday]

Hi all!

Thank you all so much for the advice and help. Sorry it's been a minute. I took everything into account, did some more research, made my purchases, and then waited and waited for a clear night. 

 

I decided my target would be the moon since it's big and bright. 

 

I first checked my imaging train and everything worked perfectly. I was able to achieve a crisp focus with my DSLR. 

 

Next the visual assembly. 

First up was a 2" spacer. Then the 2"-->1.25" adapter. Next a celestron diagonal, and then the baader eyepiece. 

 

I cannot, for the life of me achieve any sort of focus. I've created nearly every combination of location for each piece, some all the way into the tubes, some almost all the way out and vice versa. Nothing I did made the moon come into focus. Removed the spacer and just had the adapter go straight into the scope tube. It's driving me insane trying to figure it out!

 

Attached Thumbnails

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Edited by lunarmonday, 07 July 2025 - 09:19 PM.

[rjacks]

I think you misinterpreted the advice - there is no need for a spacer between the telescope and the diagonal. The respondents were noting that two-inch diagonals can be used with both 2" and 1.25" eyepieces. The diagonal itself provides the needed spacing to bring the eyepiece into focus range. See photo below. Here a 2-inch diagonal is inserted directly into the back of the focus tube. This 2-inch diagonal has an adapter for using 1.25" eyepieces. Photo shows a 1.25" eyepiece in the 2-inch diagonal. 

 

Edited by rjacks, 08 July 2025 - 08:11 AM.

[archer1960]

Hi all!

Thank you all so much for the advice and help. Sorry it's been a minute. I took everything into account, did some more research, made my purchases, and then waited and waited for a clear night. 

 

I decided my target would be the moon since it's big and bright. 

 

I first checked my imaging train and everything worked perfectly. I was able to achieve a crisp focus with my DSLR. 

 

Next the visual assembly. 

First up was a 2" spacer. Then the 2"-->1.25" adapter. Next a celestron diagonal, and then the baader eyepiece. 

 

I cannot, for the life of me achieve any sort of focus. I've created nearly every combination of location for each piece, some all the way into the tubes, some almost all the way out and vice versa. Nothing I did made the moon come into focus. Removed the spacer and just had the adapter go straight into the scope tube. It's driving me insane trying to figure it out!

Can you show us the setup you use for your DSLR? That will help us determine if you need to move the EP closer or farther from the OTA. Given what I've seen so far, I'm thinking you are running out of in-focus, not out-focus.

[PKDfan]

Hi all!
Thank you all so much for the advice and help. Sorry it's been a minute. I took everything into account, did some more research, made my purchases, and then waited and waited for a clear night.

I decided my target would be the moon since it's big and bright.

I first checked my imaging train and everything worked perfectly. I was able to achieve a crisp focus with my DSLR.

Next the visual assembly.
First up was a 2" spacer. Then the 2"-->1.25" adapter. Next a celestron diagonal, and then the baader eyepiece.

I cannot, for the life of me achieve any sort of focus. I've created nearly every combination of location for each piece, some all the way into the tubes, some almost all the way out and vice versa. Nothing I did made the moon come into focus. Removed the spacer and just had the adapter go straight into the scope tube. It's driving me insane trying to figure it out!

Yes drop that spacer ahead of the diagonal lunarmonday. You've simply pushed the image plane too far ahead.

The order should be diagonal into the optical tube then the 2"-1 1/4" adapter into the diagonal then your eyepiece.

Once thats tried all should become able to be brought to focus.

Please show us your scopes working end for us to be certain.

Cheers !!


Lance
CSS
P.s. PM me again if troubles persist. Glad to help end this frustration your having.

Edit if your using a 1 1/4" diagonal and not a 2" then place the 2"-1/14" adapter into the focuser then the diagonal into it and finally the eyepiece. If still no luck then try lifting the eyepiece out of the diagonal and see if a tidy image forms then you might need an extension tube.

Good Luck !!

Edited by PKDfan, 09 July 2025 - 12:59 PM.