Help please Canon 450d

[pianorealm]

Hi everyone, I'm really struggling with an issue involving my modded Canon 450d

It's been absolutely fine for 18 months or so but just a couple of weeks ago the problem started

I can't get sharp focus now (it's always used with Celestron C8)

It's not a focus travel problem, as when attempting to focus it does get close to focus then goes out again. Just doesn't get to 'sharp focus'.

I don't even get close enough really to use the bahtinov mask

Visual observing is fine so it's not a scope problem

The setup is housed in an observatory with de-humidifier on 24/7 and I hadn't even moved or changed anything before the problem started

Tried a factory reset but to no avail

I realise DSLR's often have 'auto focus' issues but obviously that's not the case here

Really hope someone might be able to help or advise if they have had a similar problem?

Many thanks, Howard

[michael8554]

Hi Howard,

What are you looking at when you are focussing?

Dslr viewfinder? Dslr Liveview screen? Liveview on a monitor?

Has the camera been set to a low resolution setting by mistake?

A jpg of your poor focus would help

Despite your dehumidifier I would check C8 and camera sensor.

Michael 

[Adam J]

Sounds like the sensor is clouded in some way to me. Try taking a flat frame also try moving the focus star to a different area of the sensor. So not the centre. 

[pianorealm]

On 2/18/2018 at 18:21, michael8554 said:

Hi Howard,

What are you looking at when you are focussing?

Dslr viewfinder? Dslr Liveview screen? Liveview on a monitor?

Has the camera been set to a low resolution setting by mistake?

A jpg of your poor focus would help

Despite your dehumidifier I would check C8 and camera sensor.

Michael 

Thanks very much for your reply Michael.

I use APT and view the image on a monitor whilst using the Bahtinov mask

So take a serious of .....usually 2 sec images and adjust focus between each

This method has worked fine before

The camera resolution is set to low whilst I do this to speed things up, but it's the way I have always done it before I switch to raw for imaging

The C8 seems fine as a visual star test with an eyepiece looks good

The sensor (or filter over it) looks very clear

I will post an image but its been cloudy here last few nights, hoping for a bit of clear this evening

Howard

[pianorealm]

On 2/19/2018 at 00:08, Adam J said:

Sounds like the sensor is clouded in some way to me. Try taking a flat frame also try moving the focus star to a different area of the sensor. So not the centre. 

Thanks very much for your reply Adam

The sensor looks to be very clear

The issue is still there no matter which part of the frame the focus star is in?

Just don't understand as this issue just suddenly started

I'll persevere.....there's obviously a reason for it.....probably staring me in the face!

[michael8554]

4 hours ago, pianorealm said:

So I take a serious of .....usually 2 sec images and adjust focus between each

That's not the best way to adjust focus !

Set to max ISO and Raw and turn on Liveview.

This gives a continuous image so you see focus change as you adjust.

When close to best focus turn on the magnifier to fine tune.

Michael