Opticstar AR80S problems

[moriniboy]

I recently bought this scope for £60, bargain I thought, however first light brought the realisation that focus, especially on Jupiter was well below par with soft views at high mag and an offset halo of light.

I thought it may be down to the fact that its an F5 achro but a friend also has the scope and this was performing perfectly.

Not being one to give up on a scope I duly removed the lenses and cleaned them on all faces as the previous owner was a smoker - no improvement, the problems were still present.

As the halo was offset and defocused star showed a pretty miserable star test I decided to replace the air gap spacer with three pads 0.75mm deep (i.e. same depth). Now we are getting somewhere, the halo was still present but it was now central and the star test showed collimation was fine.

I decided that the 0.75mm spacer was probably the culprit and experimented with various thicknesses of spacer, I'm now at 1.0mm thick and the halo has gone, Jupiter's bands are now visible using a zoom ep set at 7.2mm and its focusing really well.

All I can assume is at the factory someone used the wrong spacer thickness, simple as that and it may only be a problem with the older models like mine (tube ringed version) not the newer rotatable focuser models.

Give it a go, its a great scope and simples to fix.

[Uplooker]

Nigel,

Well done that man, glad you got it sorted. It does seem a strange anomaly.

[John]

Thats an interesting and useful post

I've read of a number of issues with these scopes including Neil English's example. He ended up putting a Skywatcher ST80 objective in it, which was an improvement.

Playing around with spacer thickness and rotating the lens elements relative to each other are treatments that I've seen used for other refractors with issues as well. Takes some confidence to do though, especially if you are new to the hobby.

[moriniboy]

Sorry, yes simples to me as I have spent all my life taking things to bits to see how they worked....

[moriniboy]

Well seeing as I sorted out the optics which are the most important bit I decided to give the scope a bit more TLC.

As shown on the Astronomy Shed videos I noticed that the flat that the focuser shaft bears onto was concave an not actually flat.

Using an oilstone I gently cut away the high points until it was flat (notice deep area which I did not consider was worth removing as It may have compromised the integrity of the focuser tube)

Installed back in position and a lot smoother.

Finally as I had it in bits I flocked in front of the first and second baffles leaving the final area with a paint finish as original.

Finished article, I'm off out to star test it 

[robmichael81]

Well seeing as I sorted out the optics which are the most important bit I decided to give the scope a bit more TLC.

As shown on the Astronomy Shed videos I noticed that the flat that the focuser shaft bears onto was concave an not actually flat.

P1050827.JPG

Using an oilstone I gently cut away the high points until it was flat (notice deep area which I did not consider was worth removing as It may have compromised the integrity of the focuser tube)

P1050828.JPG

Installed back in position and a lot smoother.

P1050829.JPG

Finally as I had it in bits I flocked in front of the first and second baffles leaving the final area with a paint finish as original.

Finished article, I'm off out to star test it 

P1050830.JPG

Would be interested on how your getting on with this scope as I have also bought one second hand. To be honest I was thinking of just using as a guide scope.

[moriniboy]

Hi sold mine to a guy down South recently who was going to use it as a guidescope as well.

As an alternative grab and go I have now got a TeleVue Ranger which I could not resist as its a lightweight 1.5kg compared to the Opticstar's 2.1kg