Harrys Vids


I have been asked by a few users about more vids , so lets have everybody’s wish list
I would like to keep it in the tradition of my vids I,e 1 subject at a time so I can keep the vids as concise as I can.

How to set up the local version of astronomy net seems a popular suggestion

And over to you for suggestions

King Regards

Harry Page

I would also think profile setup is a key one as, getting your image scale right, guiding integration etc. and how to use them efficiently. I been helping out a few people recently who jump in the middle and moan their settings are not saved.

Auto focus settings and how to get them right.


I agree on the profile setup , this is on the soon list also the auto focus suggestion is great , just have to learn how
to do it :smile:

Well worth it. IMHO, SGP has the best autofocus I have seen so far, at least for LRGB (FocusMax may be slightly better for narrowband as it can go to a brighter star instead of using offsets). The idea of using more than one star makes it more robust, especially in poor seeing, IMHO. It is bad enough to have larger stars due to bad seeing without compounding that with less than ideal focus.

Yes I do use it , but it worked for me at the default setting so I did not learn how to
work out the tech way to set it up
Something I will now do


I found that my calculated step size was 5, but I needed a size of 20 to get a good v curve. What I really must learn is focusing by offset from a filter. This would be such a time saver as I tend to use 9 points and 30s exposures for narrowband. Would be great if you could include that in a vid :slight_smile:

Pretty easy, really. Just make sure that you have the default focus positions correct for each filter by doing several check runs at the same temp. and then check the two boxes indicated and select lumininance (or whatever) for your focus filter. It will apply the difference between the filter used to focus and the one used to image after if focuses and before it images.

Thank you @CCDMan. Seems straightforward, I just need to work out the relative offsets. I think it would still be a nice feature to ‘nod at’ during a video - Harry’s SGPro vids really show how simple the capturing process can become…

If you do go down the auto focus path we’re now suggesting that the High HFR value should be 3X the low (in focus) HFR value when viewed on the graph. The previous instructions about microns and all that are too complex and can be difficult to get right. The “3X” value works well and is fairly easy to get figured out rather than the math based solution which is also for a now out dated auto focus method. Also 3X isn’t a hard and fast number…just get close and you’ll be fine. (And since I know someone will ask “what is close?” get between 3x and 5x) :smile:

This will be reflected in future documentation.


1 Like

Hi Jared

that sounds good to me , I like to avoid complex instructions people get bored :smile:


Is all this focus by filter really necessary if you have par-focal filters? Just got my STT-8300M with 7 Baader filters yesterday, so I am a complete newbie using filters. Doesn’t par-focal mean they will all use the same focus point?

If your filters are TRULY par-focal then there is no need to refocus or setup offsets…however “par-focal” doesn’t always seem to be truly par-focal. Filters that are par-focal at F/11 may not be at F/2.8. I would recommend verifying that they’re actually par-focal with your system rather than just taking their word for it. Other than the actual glass other things can shift focus like tilt in your filter wheel.

For example the focus offset for my “par-focal” narrowband filters is about 90 steps…which is around 2X my CFZ…I wouldn’t consider this par-focal even though the manufacturer states they are. But I also can’t tell you 100% that it’s the filter’s fault…


I would also add that any refractive element can have enough chromatic aberration that even if the filters are parfocal, the system as a whole will still not be exactly parfocal. So basically you can have parfocal filters that wind up effectively not being parfocal.

My filters ( baader) say they are parfocal and with all mirror systems they are , but not with a refractor

so best get your self a good newt



As with almost everything in this hobby “it depends.” As a general rule
though, I would say to NOT rely on the parfocal-ness of filters for tack
sharp focus. I’ve read in other places that the refraction properties of
the telescope optics may affect the focus point for different wavelengths
of light, so even if the filters are parfocal the scope optics may cause
differences in focal points (or something like that…I don’t understand
all this either!).

I have astrodon filters and for a long time I simply used the LUM filter
for focus (without offsets) because I thought the filters were parfocal.
Since I’ve started using offsets I believe that my focus has improved, and
there was enough of a difference that even my parfocal filters benefited
from using offsets so that the focus points are slightly different for each

Amen. Rule of thumb for me is either use offsets or focus thru the filter being imaged thru.