Qhy8l

[Stu Wilson]

I'm about to purchase a 2nd hand QHY8L.

Can anyone please tell me how and when to use the desicant tube?

 

Cheers

 

Stu

[Thalestris24]

28 minutes ago, Stu Wilson said:

I'm about to purchase a 2nd hand QHY8L.

Can anyone please tell me how and when to use the desicant tube?

 

Cheers

 

Stu

Hi Stu

If you don't undo it you probably never need to use it. Otherwise I think you just put some orange silica gel desiccant beads in it. Change them if they ever change to green. I'm sure there are some instructions in the manual...

Louise

[Stu Wilson]

16 hours ago, Thalestris24 said:

Hi Stu

If you don't undo it you probably never need to use it. Otherwise I think you just put some orange silica gel desiccant beads in it. Change them if they ever change to green. I'm sure there are some instructions in the manual...

Louise

Cheers.

Hopefully arrives tomorrow so I'll find out.

[Thalestris24]

Here is manual:

QHY8L user manual.pdf

or

QHY8L Camera Manual.pdf

Louise

[Stu Wilson]

Thanks for the help.

[Stu Wilson]

On 04/04/2018 at 12:43, Thalestris24 said:

Here is manual:

QHY8L user manual.pdf

or

QHY8L Camera Manual.pdf

Louise

Hi again Louise.

Not having much luck so far.

Skies are very poor.

Have you any idea how far the draw tube should be coming out of the OTA with this camera to achieve focus? (Sw200p with short Crayford focused with built in extension tube if required).

I haven' even managed to see a blurry star in preview mode. Think the settings are probably all wrong too. Serious lack of info with this camera is is there any certain gain and offset settings to use with preview to actually see something?

Thanks for any help.

[Thalestris24]

Hi

I've not used mine in over 2 yrs so can't remember much out of the top of my head. There are instructions on setting the gain and offset in the manual. I think the front of the camera has a 20mm backfocus to the sensor. Exact spacing will depend on whether you're using a plain coma corrector or a reducer. You might need to try it and see.  Sometimes projecting a bright image e.g. the moon or distant daytime object, on to some tracing paper can help to show where the focus is.

Hth

Louise

[JSeaman]

This might help:

 

 

You may need a diagonal without a field flattener/focal reducer and a gain of 0, offset of 120 should get you started

[Stu Wilson]

Thanks for input.

I had a big learning curve with DSLR but I'm thinking I'm back at square 1 lol

[Stu Wilson]

1 hour ago, JSeaman said:

This might help:

 

 

You may need a diagonal without a field flattener/focal reducer and a gain of 0, offset of 120 should get you started

The skywatcher low profile crayford focused I use has an extension tube built in. Will this need to be drawn out quite far?

[JSeaman]

I have very recently gone through the same learning curve, it really isn't too bad. I spent a day inside working out the gain and offset and getting all the drivers set up and understanding the (fickle) power up procedure so my first night out wouldn't be a complete failure! There is a learning curve but it's not too bad, be methodical when it goes wrong is the best tip I could offer, change one thing at a time and you'll find it works out I'm sure. 

As for the draw tube, I was on an ED80 and I couldn't come close to focus with it fully extended and even with a small extension. I used a diagonal to get me up and running but picked up a focal reducer at the weekend which I'll fit if the clouds ever disappear!

[Stu Wilson]

11 minutes ago, JSeaman said:

I have very recently gone through the same learning curve, it really isn't too bad. I spent a day inside working out the gain and offset and getting all the drivers set up and understanding the (fickle) power up procedure so my first night out wouldn't be a complete failure! There is a learning curve but it's not too bad, be methodical when it goes wrong is the best tip I could offer, change one thing at a time and you'll find it works out I'm sure. 

As for the draw tube, I was on an ED80 and I couldn't come close to focus with it fully extended and even with a small extension. I used a diagonal to get me up and running but picked up a focal reducer at the weekend which I'll fit if the clouds ever disappear!

What diagonal did you use? How much backward distance did you gain?

[sloz1664]

10 hours ago, Stu Wilson said:

Hi again Louise.

Not having much luck so far.

Skies are very poor.

Have you any idea how far the draw tube should be coming out of the OTA with this camera to achieve focus? (Sw200p with short Crayford focused with built in extension tube if required).

I haven' even managed to see a blurry star in preview mode. Think the settings are probably all wrong too. Serious lack of info with this camera is is there any certain gain and offset settings to use with preview to actually see something?

Thanks for any help.

Regards focus you can achieve this during daylight hours, on a distant object like a TV aerial. You will probably need to use very short exposures or if it's too over exposed mask the front of your scope and add a small hole in the centre of the mask to let the light in. I'd set the gain initially at 8 and offset 120. There is a proceedure for setting the gain and offset, which again can be carried out indoors.

Gain & Offset.pdf

Steve

 

[Stu Wilson]

11 minutes ago, sloz1664 said:

Regards focus you can achieve this during daylight hours, on a distant object like a TV aerial. You will probably need to use very short exposures or if it's too over exposed mask the front of your scope and add a small hole in the centre of the mask to let the light in. I'd set the gain initially at 8 and offset 120. There is a proceedure for setting the gain and offset, which again can be carried out indoors.

Gain & Offset.pdf

Steve

 

Thanks guys.

I' going to try the daylight thing after work (if it's not raining) and I suppose this way I'll know if I need an extension tube added into the train.

[JSeaman]

I just used the std skywatcher diagonal that comes with the ED80

Absolutely to setting it up in daylight. Note that the offset and bias figures are recommended in the QHY8L manual which also tells you the set up process

[sloz1664]

4 minutes ago, Stu Wilson said:

Thanks guys.

I' going to try the daylight thing after work (if it's not raining) and I suppose this way I'll know if I need an extension tube added into the train.

You will need an extension tube. You could use your diagonal to help achieve focus, but I wouldn't use it for imaging. You will need spacer(s) for the specified length. With it having a large chip & to gain a nice flat field you will probably need a coma corrector.

Steve

[david_taurus83]

If it's the same low profile focuser I fitted to my F5 200p then I have measured 42mm from the focuser body to the top of the extension tube for bringing my Canon 600d into focus. I know the sensor depths will be different but that 42mm plus say 11/12mm for the bayonet ring plus the depth from bayonet face to sensor should give you an idea of where the focal point is with that focuser on an F5 200p. I'm sure someone on here will know the 600d depth to sensor as I can't find it on a quick Google!

 

Good luck.

[Stu Wilson]

My focused has a built in extension tube but not sure how far it comes out.

[Thalestris24]

Hi again Stu

You don't want a diagonal - just an extension tube. Preferably an adjustable one. If you've had the scope in focus before with a dslr, then you just need to do a simple calculation - the back focus of your dslr + t-ring, minus the 20mm back focus of the qhy8l. The difference is the length of extension tube you'll need (making some allowances). So if with your dslr the backfocus was (for example) 55mm then you'll need an extension tube of about 55-20mm = about 35mm. With that in place you'll be able to focus as if you just had the dslr fitted  It is a bit more fiddly using a cooled ccd after using a dslr - one reason I stopped using mine! As it happens, I'm waiting for an adjustable extension tube so I can connect the qhy8l up again but with my 115mm frac instead. You do have to wait some time for the qhy8l to cool to a stable temperature (and to warm up again!) but, being cooled, you can take long exposures ok and obviously without all the thermal noise you get with an uncooled dslr. As I recall, with longer exposures, there was some amp glow but taking some darks deal with it. You only have to set the gain and offset once - thereafter you use the same values each time. Qhy's EZCap is good for setting gain and offset - mine came out to gain = 13, offset = 118. The values aren't critical but the correct ones give you the best dynamic range. With the Ascom driver, APT is good for taking images and handles the cooling.

Louise

ps you don't want your focus tube out too far as you want everything to be tight and rigid. So it's better to add in an extension tube and keep the focus travel short.

[Stu Wilson]

4 minutes ago, Thalestris24 said:

Hi again Stu

You don't want a diagonal - just an extension tube. Preferably an adjustable one. If you've had the scope in focus before with a dslr, then you just need to do a simple calculation - the back focus of your dslr + t-ring, minus the 20mm back focus of the qhy8l. The difference is the length of extension tube you'll need (making some allowances). So if with your dslr the backfocus was (for example) 55mm then you'll need an extension tube of about 55-20mm = about 35mm. With that in place you'll be able to focus as if you just had the dslr fitted  It is a bit more fiddly using a cooled ccd after using a dslr - one reason I stopped using mine! As it happens, I'm waiting for an adjustable extension tube so I can connect the qhy8l up again but with my 115mm frac instead. You do have to wait some time for the qhy8l to cool to a stable temperature (and to warm up again!) but, being cooled, you can take long exposures ok and obviously without all the thermal noise you get with an uncooled dslr. As I recall, with longer exposures, there was some amp glow but taking some darks deal with it. You only have to set the gain and offset once - thereafter you use the same values each time. Qhy's EZCap is good for setting gain and offset - mine came out to gain = 13, offset = 118. The values aren't critical but the correct ones give you the best dynamic range. With the Ascom driver, APT is good for taking images and handles the cooling.

Louise

Cheers Louise.

Here' the focused I use. I' pretty sure I should get close with the built in extension.

https://www.astroshop.eu/focusers/skywatcher-dual-speed-2-low-profile-crayford-focuser-for-newtonian-reflectors/p,16119

 

[Thalestris24]

2 minutes ago, Stu Wilson said:

Cheers Louise.

Here' the focused I use. I' pretty sure I should get close with the built in extension.

https://www.astroshop.eu/focusers/skywatcher-dual-speed-2-low-profile-crayford-focuser-for-newtonian-reflectors/p,16119

 

Yes, that's the focuser you get with the SW pds scopes. You should be able to reach focus using that without an extension tube. I would set it up during the day if you can see a suitable distant object.

[Stu Wilson]

14 minutes ago, Thalestris24 said:

Yes, that's the focuser you get with the SW pds scopes. You should be able to reach focus using that without an extension tube. I would set it up during the day if you can see a suitable distant object.

Going to try after work. I'l post result.

[Stu Wilson]

Managed a try tonight.

As clouds were coming over I got focus or near enough on a star.

I had to use a spacer too but overall distance back from focuser to sensor is approx 75mm. That' with no coma corrector or reducer fitted.

Anyway thanks all for help so far. I'm sure I'll need much more in due course but hopefully some clear skies soon :-)