Should i use a UV filter for PHD2 guiding?

[bluesilver]

Hi,  Just interesting to here some thoughts on if it is worth while using a UV cut filter when guiding using PHD2

I am using an Orion 600 guide scope and the guide camera is the ASI 290mm mini

Would it be worth while running a UV cut filter with this setup or would i not see any benefit from doing so?

I was looking at one of the ZWO UV cut filters,  actually it is the one that i use on my camera that i use when imaging the planets.

Sky is a reasonably dark area,  around Bortle 2-3

Any advice would be greatly appreciated.

Thanks.

 

[Budgie1]

I use a UV/IR cut filter on my guide ASI120MM Mini guide camera as I found it just makes the image a little clearer. It also has the benefit of protecting the sensor from dust etc.

I know the focus doesn't have to be pin-point for guiding but I like to get it as good as I can, and the UV/IR cut filter helps with this. I use the ZWO filter as it cheap and does the job.

[CloudMagnet]

I have the same as @Budgie1 above, I think it does make a small improvement to the guiding. The explanation I suppose is down to the star profile the PHD is looking at to identify any movement in the guide star, if you take away the UV/IR light that isn't correclty focused then it SHOULD provide cleaner data for PHD to use.

Small differences in fairness but given the amount of time and effort that goes into guding, it seems a cheap price to pay.

[michael8554]

IR cut filters are often suggested to improve refractor images, I've not heard of UV being a problem.

Michael

[Skipper Billy]

I use a cheap IR cut filter (ZWO) on my guide camera (Lodestar) and the star image is definitely a little tighter - whether that helps PHD2 or not I cant tell but I would imagine it should??

[ollypenrice]

The original wisdom was that PHD worked best with a soft focus, this coming from Craig Stark himself. However, I've read since then that the software now prefers a sharp focus. I think it's all to do with how the notional centroid of the star is being calculated.

As ever, I'd give it a try and report back.

Olly

[fifeskies]

ZWO UV/IR on my 290mm mini guidecam did make the stars a whole lot tighter.

With PHD2 multi-star guiding it is hard to say if it changed the accuracy.

I got the filter 2nd hand so wasn't a big outlay and the guide cam monitor window is much clearer.

[david_taurus83]

Same here. I was struggling to find a good focus on one of my guide scopes. Stars always looked too bloated in PHD for my liking. Bought a cheap IR/UV cut filter and it works great. I would even say try and find the cheaper SVBony ones as they work just as well.

[Jonk]

Or. and this worked for me very well in the past - use a red filter.

[CCD-Freak]

I have been using a UV-IR cut filter with my guide camera for years.  I makes the stars appear less bloated and the guiding seems a bit better.

 

[vlaiv]

How about using IR pass instead?

IR part of spectrum is the least susceptible to seeing. 800nm + range won't be as "spread" over focal range to result in bloated stars (it will be focus shifted - but you can refocus to it).

Some cameras - especially some OSC models - have good / uniform QE over 800nm.

[CloudMagnet]

On 20/11/2021 at 17:29, vlaiv said:

How about using IR pass instead?

IR part of spectrum is the least susceptible to seeing. 800nm + range won't be as "spread" over focal range to result in bloated stars (it will be focus shifted - but you can refocus to it).

Some cameras - especially some OSC models - have good / uniform QE over 800nm.

Interesting idea, you would still be able to focus without any issue (would require a very small adjustment) and as long as the QE of the camera was high enough to produce a good enough SNR then PHD2 wouldn't know the difference.

Could be interesting if the guiding would be affected by high cloud. I would assume that this setup would be more susceptible to losing the star as cloud tends to absorb IR well, whereas visible light tends to hold up better.