SV205 focus issue - what am I doing wrong.

[Starslayer]

Mmmm. Really not sure.  I tried the SVBony SV205 last night on the moon with SW ST202  F5 / 500 - using sharpcap on windows 10. 

Lined the almost full moon centre ep. Swapped out to camera and almost nothing from one end of focuser travel to the other. I say almost as I occasionally saw what may have been the outer edge or something large but all black . dark green and not much else. Just a hint of curvature.  Ensured moon still in view several times. Played with gain and exposure etc but still nothing at all.  Is this a focus issue perhaps? I know the camera isn't the best but I should at least be able to capture the moon. The scope should be suited to this so I can think of nothing else other than I may need to be putting some kit in the focus line somewhere.  Works fine in daytime on distant trees etc.  I am really getting nowhere with this camera on what should be an ideal scope for it and for me as a beginner at least to capture some lunar if nothing else. 

Puzzled. 

[StevieDvd]

Set the camera up in the scope and focus on distant trees and leave the focuser locked for a night viewing. That tells us that the focusing is possible so the issue is most likely the exposure being to bright  and overwhelming the view.  Try with the shortest exposure settings and a street light as a target, the moon would need a shorter exposure but the street light will let you practise.

If that works check the edge of the moon and you should only need minor changes to get correct focus and exposure.

 

[Starslayer]

14 minutes ago, StevieDvd said:

Set the camera up in the scope and focus on distant trees and leave the focuser locked for a night viewing. That tells us that the focusing is possible so the issue is most likely the exposure being to bright  and overwhelming the view.  Try with the shortest exposure settings and a street light as a target, the moon would need a shorter exposure but the street light will let you practise.

If that works check the edge of the moon and you should only need minor changes to get correct focus and exposure.

 

Erm, thank you. I think I understand. Only issue there is I have a street light but it is very close, probably too close as in the middle of our cul de sac. May be able to try on distant windows with lights on - may have to be a tad careful there though.  🙃

[Adam J]

1 hour ago, Starslayer said:

Mmmm. Really not sure.  I tried the SVBony SV205 last night on the moon with SW ST202  F5 / 500 - using sharpcap on windows 10. 

Lined the almost full moon centre ep. Swapped out to camera and almost nothing from one end of focuser travel to the other. I say almost as I occasionally saw what may have been the outer edge or something large but all black . dark green and not much else. Just a hint of curvature.  Ensured moon still in view several times. Played with gain and exposure etc but still nothing at all.  Is this a focus issue perhaps? I know the camera isn't the best but I should at least be able to capture the moon. The scope should be suited to this so I can think of nothing else other than I may need to be putting some kit in the focus line somewhere.  Works fine in daytime on distant trees etc.  I am really getting nowhere with this camera on what should be an ideal scope for it and for me as a beginner at least to capture some lunar if nothing else. 

Puzzled. 

Do you have a diagonal that you would normally use  with your scope? If so the diagonal increases the light path and  effectively extends the focus travel outwards like an extension tube would, try putting the camera into the diagonal and attached to the scope and see if you can reach focus then. If that is the case you may want to get a 1.25 inch extension tube so that you can image without the diagonal. 

 

Adam 

Edited November 18, 2021 by Adam J

[Starslayer]

6 minutes ago, Adam J said:

Do you have a diagonal that you would normally use  with your scope? If so the diagonal increases the light path and  effectively extends the focus travel outwards like an extension tube would, try putting the camera into the diagonal and attached to the scope and see if you can reach focus then. If that is the case you may want to get a 1.25 inch extension tube so that you can image without the diagonal. 

 

Adam 

I was always trying it with the camera in the supplied diagonal. Pop out the ep after centering the target, pop in the camera.  No joy.. I did also try last night to remove diagonal and pop camera straight into the focuser bit.. Again - no joy.   I actually finished by using my iphone on attachment and got some nice video and pics although the weight is no good for this set up at that end.  Makes me want to ditch the cam for a decent entry level ZWO but something makes me think that is not the answer. 

Edited November 18, 2021 by Starslayer

[Adam J]

3 minutes ago, Starslayer said:

I was always trying it with the camera in the supplied diagonal. Pop out the ep after centering the target, pop in the camera.  No joy.. I did also try last night to remove diagonal and pop camera straight into the focuser bit.. Again - no joy. 

If you can get an image in daylight then its not likely to be the camera. Even out of focus if you are seeing the image dim as you move your hand over the front of the scope then the camera is working. After that the only remaining thing it can be is that you are not reaching focus. You could try manually pulling the camera backwards from the end of the eyepiece holder on the diagonal but in the end its most likely you dont have sufficient outward travel. 

[Starslayer]

1 minute ago, Adam J said:

If you can get an image in daylight then its not likely to be the camera. Even out of focus if you are seeing the image dim as you move your hand over the front of the scope then the camera is working. After that the only remaining thing it can be is that you are not reaching focus. You could try manually pulling the camera backwards from the end of the eyepiece holder on the diagonal but in the end its most likely you dont have sufficient outward travel. 

 

Noted - I also have a 6" sct so will try with that when the nights are better.   I assumed that the 102 would be good for this this type of entry level thing but hey.................. 

[PadrePeace]

I’ve had this kind of issue and will guarantee you don’t have the camera back focus set correctly as others have suggested. Replacing an eyepiece with the camera or removing the diagonal and replacing it with the camera will leave your sensor so far out of focus you will get nothing but dark areas or blurred shadows. Follow Adam J’s advice and get your sensor far enough back to focus the light cone into it. You may well need extension tubes to do this as I have scopes that have a lot of additional extension tubes fitted to the back of the focuser to get focus. See examples attached. Do the back focus math for your camera, set that distance and all will become clear… literally.

[Starslayer]

9 hours ago, PadrePeace said:

I’ve had this kind of issue and will guarantee you don’t have the camera back focus set correctly as others have suggested. Replacing an eyepiece with the camera or removing the diagonal and replacing it with the camera will leave your sensor so far out of focus you will get nothing but dark areas or blurred shadows. Follow Adam J’s advice and get your sensor far enough back to focus the light cone into it. You may well need extension tubes to do this as I have scopes that have a lot of additional extension tubes fitted to the back of the focuser to get focus. See examples attached. Do the back focus math for your camera, set that distance and all will become clear… literally.

Excellent.  Thank you for your explanation and time putting up pictures. Is there an idiots guide somewhere regarding “ doing the math”.? 

[PadrePeace]

Google Back focus and pick any of the many YouTube guides to setting this up.

Your camera will have a required back focus distance. This is generally 55mm and is measured from the sensor inside the camera and not the camera case. If you are using a Flattener and/or a reducer on your scope 55mm is measured from the camera side of that device to your sensor. This is where you will need extension tubes/adaptors as you see in my pics. To get an idea of how far your sensor is mounted inside the case you’ll need to find this online or ask on this forum. It’s quite straightforward really.

The reason astrophotographers have to add this additional back focus distance is because scopes are always made to work for visual observing as well and therefore have the focuser optimised accordingly. This is why your eyepieces work but the camera has issues because it’s too close to the scope lens by a significant amount.
 

If you are not using a flattener/reducer you may just be able to extend the focus tube out enough to reach sensor back focus but often that is not the case and you need adapters that screw together to bridge the additional gap.

Edited November 19, 2021 by PadrePeace

[PadrePeace]

Just re read your opening comment to this thread where you say ‘it works fine on trees during the daytime’ please clarify if you mean the EP or the camera?

what camera are you using?

[Cosmic Geoff]

I managed to fit a Canon 300D camera to a Startravel ST102.  It needed a T2 extension tube about 2 inches long to make it work.

I regulary use the scope with a ASI224MC camera and a SVbony helical focuser (no diagonal or extensions).

[bosun21]

I know that the attention is mainly on back focus but this guy on YouTube uses the SVbony 105 & 205 and he highlights the following problems he encountered 

https://youtu.be/IZJV7a9rAaU

 

[Starslayer]

27 minutes ago, PadrePeace said:

Just re read your opening comment to this thread where you say ‘it works fine on trees during the daytime’ please clarify if you mean the EP or the camera?

what camera are you using?

Both ep and camera are fine in daylight but of course I am focussing on trees etc that are far closer than anything 'up there'.   It is the SVBony SV205

[Starslayer]

4 minutes ago, bosun21 said:

I know that the attention is mainly on back focus but this guy on YouTube uses the SVbony 105 & 205 and he highlights the following problems he encountered 

https://youtu.be/IZJV7a9rAaU

 

Haha thank you. I had seen that and had actually posted in there regarding issues I had with the software etc. 

[StevieDvd]

If you can focus both the camera and eyepiece on distant trees then that is good.  It's likely though that you don't have the same focus position for the camera and eyepiece.

During the day do the same focus on a distant object with the camera fully inserted and note how far the focuser has extended. Measure with a ruler if the focuser does not have markings.

Hopefully, you will be able to focus correctly but still have the ability to move the focuser either way.  If your focuser is fully extended and you need to pull the camera out of the diagonal little then that means an extender could be required - this is typical when you don't use a diagonal with the camera.

A good tip I was given in my early use of cameras on scopes was to have an eyepiece that had the same focus as the camera.  You focus with the camera and lock the focuser position, then take the camera out and try an eyepiece - you need one that only focuses when it is not fully inserted.   This is called a parfocal eyepiece for the camera but you have to be able to put the eyepiece in the same position each time.  You'll a small ring that fits over the eyepiece nose which can be kept in place (may have come with a camera) or else try a ziplock. Now you centre and focus using the eyepiece and just switch over to the camera when needed.

 

[Starslayer]

I understand what you mean but.........  the picture here shows the camera focussed on a tree a good half mile away.  The difference between this and a 10mm ep focussed is barely a quarter turn. Note that I have a good 30mm travel left inwards and more than that outwards on the focuser.  This is again makes me think it is something in the capture settings but I have played around with these to the point of despair and just gone back to visual. 🥶

Edit - I have now 'gained access' to the top level of the house and redone the procedure on the flag on top of our local hospital over 2 miles away. Again, very little difference in travel to focus the camera from the ep setting using 10mm and only the quarter turn between 10mm and 25mm. Weather is rubbish but I am set up in the top velux in case I get a lunar glimpse later.  Have got the appropriate pencil marks on the focuser too. 

Edited November 19, 2021 by Starslayer

[StevieDvd]

1 hour ago, Starslayer said:

I understand what you mean but.........  the picture here shows the camera focussed on a tree a good half mile away.  The difference between this and a 10mm ep focussed is barely a quarter turn. Note that I have a good 30mm travel left inwards and more than that outwards on the focuser.  This is again makes me think it is something in the capture settings but I have played around with these to the point of despair and just gone back to visual. 🥶

Yep that clarifies it as not being a lack of focus adjustment.  From a quick google the only other thing I found was the settings in Sharpcap and unchecking an option which limits the exposure settings see here on CN

As SVBony use Sharpcap themselves in their blogs and manual it must be a valid combination.

There is an updated driver and other links on the SVBony site here which may be worth trying as well.

 

 

[Starslayer]

17 minutes ago, StevieDvd said:

Yep that clarifies it as not being a lack of focus adjustment.  From a quick google the only other thing I found was the settings in Sharpcap and unchecking an option which limits the exposure settings see here on CN

As SVBony use Sharpcap themselves in their blogs and manual it must be a valid combination.

There is an updated driver and other links on the SVBony site here which may be worth trying as well.

 

 

Thank you. Will go 'see". Pretty sure my driver is up to date ( will check ) and I already have the auto unchecked so I can play with the settings.  

Edited November 19, 2021 by Starslayer

[AstroMuni]

1 hour ago, Starslayer said:

Thank you. Will go 'see". Pretty sure my driver is up to date ( will check ) and I already have the auto unchecked so I can play with the settings.  

You should be able to get near focus in daylight. If thats not working then it will be quite challenging at night. Thats my experience.

During daytime use a very low exposure less than a sec.