C8, C9.25, or sw ED120

[Grotemobile]

This is the way I sorted my scope out using the star  Sirius as  a collimation  point. Only needed

to do it once. 2 years on , still ok.

[festoon]

22 minutes ago, ecuador said:

I had settled in an ED80 + a C8 for my main scopes, until I came across an inexpensive second hand C9.25 XLT and I did an upgrade from C8 -> C9.25 for less than £300 difference, not expecting a huge difference... And yet there was! I am not sure why, maybe it has to do with the fact that the C9.25 is easier to collimate (the C8 seemed to require much more precision to give the best image) and holds collimation well, maybe the claims about the different design with a slower main mirror that gives a sharper image hold water, maybe my C8 which was older was not a great specimen, but the planetary views are obviously better and you get more perks, like the baffle tube being wider so you actually can get a WIDER FoV than the C8 with the appropriate eyepiece (see here) - or less vignetting with the f/6.3 reducer if you are imaging. So, if you ever have the chance of doing a low-cost upgrade to a C9.25, I suggest you take it.

That said, I am more of an imaging person. For a person who is more into observing, apart from planets where the C9.25 has the edge, the views of an APO are stunning and the 120 ED would be a great addition to your arsenal.  So, I guess my suggestion would be probably go for the 120ED if you are more into observing, but keep an eye open for C9.25 deals to do that as well if you ever get the chance  

Now, back to collimation. Forget about doing it by hand, especially if your C8 is like mine and needs more precision than seeing would allow and doesn't hold it in general - yes I also had bob's knobs. Just use metaguide with your QHY camera. Not only will metaguide stack live so it will "beat" seeing conditions, but if your mount is a tracking mount, then it can also follow the star as you are doing adjustments and it tries to leave the FoV. But a C9.25 in my experience will be even easier (still with metaguide of course).

This is really helpful advice, thank you. I never realised that potentially a C925 could be easier to collimate compared to a C8. And I have never come across before metaguide. Just taken a look online now. Seems a little complicated looking at the instructions but hopefully it will not be too difficult with my QHY and EQ6 pro mount. Is it possible to do this indoors with a artificial star to save time?

[festoon]

7 minutes ago, Grotemobile said:

This is the way I sorted my scope out using the star  Sirius as  a collimation  point. Only needed

to do it once. 2 years on , still ok.

Hi Steve, Thank you for the video. Sorry just to confirm are you using an artificial star from Sirius (Hubble Optics) or the actual star Sirius

[ecuador]

Just now, festoon said:

This is really helpful advice, thank you. I never realised that potentially a C925 could be easier to collimate compared to a C8. And I have never come across before metaguide. Just taken a look online now. Seems a little complicated looking at the instructions but hopefully it will not be too difficult with my QHY and EQ6 pro mount. Is it possible to do this indoors with a artificial star to save time?

Again, I only had one specimen of each, so I cannot be positive that I can generalize, but especially when doing planetary imaging with the C8 it was easy to see a difference from collimating out of focus (like the above video suggests) to going in-focus (which is not often possible - hence metaguide comes in), while the C9.25 seems to be a bit more tolerant. And it doesn't lose colimation when moving it, but maybe that's not a C8 vs C9.25 thing.

Metaguide will be confusing the first time you set it up, and it should be simple afterwards. I haven't tried with an arti-star, since for the C9.25 I need a substantial distance (30m perhaps?) which I don't have at my location, so I can't tell you whether the tracking feature will work on metaguide with a stationary arti-star to help you automatically keep it centered while you collimate. Also, I assume that tracking with the EQ6 would require connection via EQMOD? Again, not something I've tried, sorry.

[John]

Artificial stars can be used but they tend to need to be placed quite a long way from the scope to work accurately so gardens are more use unless you have a very large house !

I think the distance needed for an F/10 scope such as an SCT is around 30 metres ?

 

[festoon]

I've learned a heck of a lot from this thread. Thank you for all your help.

A lot of good feedback for both the C9.25 and the ED120. That having an SCT and refractor are good telescopes complimenting each other. That even owning all three would be a good strategy! And that I should be a lot more patient with collimating my current C8, and that I'm not the only person who finds this difficult...and possibly go for a service to have it checked over and collimated. I never knew about metaguide...this is something I'll give a go for collimation help. As for the artificial star it sounds very tempting, but I'll need to go to the park to do this if I need 30m! Otheriwse Polaris is a good choice!

I will look into the options regarding collimating myself and having proffessionally checked my C8 and go from there   The only question I need to ask myself is can I afford to keep the ED80 and buy an ED120  

[Mr Spock]

I'd like an ED120 myself. It would go nicely with my C9.25

[Grotemobile]

2 hours ago, festoon said:

Hi Steve, Thank you for the video. Sorry just to confirm are you using an artificial star from Sirius (Hubble Optics) or the actual star Sirius

I used the actual star to do it with. Just had to adjust 2 of the screws. Lot easier

than what I thought. Very little adjustment needed. The difference it made for

imaging , was very noticeable.

[festoon]

Well it's been a rather disappointing end to the day...I had been talking with the chap selling the ed120 on Astrobuysell (also here) but unfortunately it has now been sold....so I'll keep an eye out for another or just buy a new one

after all the talk here I had my heart set on it....but not this time ?

[Chris]

1 hour ago, festoon said:

Well it's been a rather disappointing end to the day...I had been talking with the chap selling the ed120 on Astrobuysell (also here) but unfortunately it has now been sold....so I'll keep an eye out for another or just buy a new one

after all the talk here I had my heart set on it....but not this time ?

It was a rather good price, I bet a few folk where humming and haring over that one. I'm sorry you missed out though  It's a shame Skywatcher don't have the same sale on as the current Celestron sale, there are big savings on some Celestron kit at the moment...just treated myself to some 20x80 binos as a result. 

[Peter Drew]

Might be a blessing in diguise, an ED80 for wide field and a C8 for planets is a good combination. With a little care and minute tweaks you should have the C8 performing well. 

[festoon]

9 hours ago, Chris Lock said:

It was a rather good price, I bet a few folk where humming and haring over that one. I'm sorry you missed out though  It's a shame Skywatcher don't have the same sale on as the current Celestron sale, there are big savings on some Celestron kit at the moment...just treated myself to some 20x80 binos as a result. 

Thanks Chris, yes I also wish SW did the same as this celestron sale....Good choice about the 20 x 80's Hope you get some great views from them

[festoon]

Hi Peter, thats a great way of looking at it! I downloaded metaguide last night onto my laptop but will try and set up the QHY camera and mount first in my house before going outside....so I dont mess up and get used to how it works Thank you  

I'll start a new thread about this The instructions do seem a little confusing so hopefully will get some help from others on this

Eitherway, as you say I'll get my C8 tweaked and use the money I did not spend getting a proffesional clean and collimation as well. Thank you