Clarkey

Back today!!! Yey!!!!😄😄😄

4 hours ago, Lee_P said:

There are lots of RC8 telescopes out there with different branding, but they're all basically the same, right?

As far as I know there is not much between them optically. Focusers and other bits might be slightly different, but as far as I'm aware pretty much the same.

My only question is regarding cool down time with carbon tubes. My 90mm Stella refractor is very slow to cool.

52 minutes ago, 900SL said:

I was thinking around 6 nm would balance cost/performance?

On your own there. I still have the ZWO filters. Astronomik and Antila seem to get good reviews. Depends on how deep your pockets are....

I would agree with @scotty38 that the 7 slots is a definite benefit (even more so if using unmounted filters). You don't want to be opening up your filter wheel to keep changing filters. If you only do RGB or narrowband you would be OK.

As for filter sizes, I think for the 533, 1.25 are fine. For the APS-C you would probably get away with 31mm filters - but it will depend a bit on the scope and set up. I would check on the Astronomy tools website which has a filter size calculator. If you are using 'cheaper' filters then it might be worth going larger as the cost difference is small. I think you are probably better off spending the extra on better filters rather than larger.

3 hours ago, Lee_P said:

Could you explain how you get the correct backfocus with a StellaLyra RC8? I asked FLO and got this answer:

I think maybe you are over-thinking this! The 'back-focus' is just the focus point as with any other scope. For normal AP I use the four extensions provided (100mm) and then the focuser and focus normally - but the focus point is a long way back. As the primary and secondary mirrors are not moving you are not changing anything in terms of the optics. Although the supplier focuser is OK, I did change mine to a Baader ST just to make sure everything was rock solid. Not sure it was necessary really but it was nice, new and shiny😁. I don't have my rig set up at the moment, but here is a picture of roughly where my RC8 focuses (there is a tilt adjuster too which adds about 20mm).

As @Len1257 says the weight is far back. I use a combination of guidescope and homemade power box to balance.

The is also a Stella Mira flattener that might be suitable. It's design for f5 to f7 which suggests it should be ok.

Hey it's a start. It is focus and the stars are pretty round. Good start I would say.

800 iso is probably about right for the Canon. I would forget the darks and run some bias frames and flats plus increase the integration time.

In terms of framing, have a look on Stellarium or similar for some interesting areas of sky.

4 hours ago, A Scanner_darkly said:

2 welcome posts !!

Perhaps if your tone was a little less patronizing and condescending you would get a better response? 

In terms of what you are saying, whether you are right or wrong is irrelevant, you can not accuse everyone with a different view to yourself as being ignorant savages. This forum openly encourages friendly discussion and debate. If someone has a completely different view to everyone else that is accepted - not condemned or ridiculed.

How about a sky-tee with a ST120 for wide field and pick up one of the many 2nd hand 200p's for a couple of hundred pounds. Should be about on budget.

29 minutes ago, Lee_P said:

@Clarkey Could you please do me a quick favour and measure the distance from the back of your RC8 to the back of your astrocamera? I'm trying to work out if I'd need an extension pier to stop the camera-end of the telescope thwacking into my pier... Thanks!

From the back of the scope to the back of the camera - making allowances for cables and approximate point of focus - is about 43cm. Bearing in mind the back heavy nature of the scope and the width, I have never had a problem with it hitting the tripod. This is with an AZ-EQ6.

34 minutes ago, Lee_P said:

I wonder, can you use the top Vixen dovetail as a carrying handle? It's hard to tell from the pictures if you could fit your fingers underneath it to get a good grip. Maybe with some risers? The collimation does sound like a pain, but it holds well once done?

You can't use the dovetail itself as it is too close to the tube you could probably attach risers or add a handle. I actually use mine to guide with an ST80 mounted on top towards the front. Helps with the balance a bit too as the RC8's are very back-heavy once loaded with photo gear.

WRT the collimation - once set it needs very little, if any adjustment. Mine was pretty good from delivery and only really required a minor 'tweak' to give a slight improvement. In fact the images in my earlier post were taken before I collimated the scope. I wanted to wait until the end of Galaxy Season to start messing with it - just in case!

18 minutes ago, Adam J said:

Its not just the CA in itself, yes you can remove that during processing but in the end it makes the Luminescence channel less sharp because blue photons are not going exactly where you want the to go. Less important for wide field nebula work especially in narrow band, but as the OP has stated small targets (galaxies most likely) then sharpness is going to be a factor in picking up detail and if you don't have to use the L3 you are going to get allot more of those nice blues we want to see in spiral arms. I have a FPL-51 equivalent scope in the form of the FMA180 but that is very much a wide field instrument and using a L3 filter is valid. 

The often quoted "a good FPL-51 scope will outperform a poor FPL-53 scope" scenario basically relies on someone making a poor FPL-53 design, in this day and age of computer lens design and improved polishing methods you would have to try pretty hard to find such a scope. Hence, given the choice for imaging FPL-53 / FPL-55 / FCD-100 is the way to go. Moreover we know that the Starfield 102 is a good design in this case and that the above argument doesn't apply are a result. 

The other nice thing about a 4 inch F7 is that they reduce nicely to F5.5 for wider field use also. A 102mm F7 scope with access to both flatterer and reducer is a versatile imaging tool.

As I said in my post above - I don't disagree at all, I was just giving options.

I would still question the FPL-51 vs FPL-53 mainly down to the manufacturing tolerances at this price point - not specifically down to design but down to individual scopes. I have an ED80 which is FPL-53 and this gives a fair bit of blue bloat and generally this is deemed 'good' optically for the money. Mine was also optically checked by FLO.

12 minutes ago, KP82 said:

It's not only the blue bloat, but there is also loss of the details due to CA and SA with a fast ED doublet like the 110mm f/6.

Sampling with an IMX294 at 660mm with detail loss due to CA, SA and seeing, I believe the end result would be quite soft. As for the exact maths, you will have to ask @vlaiv for help.

I don't disagree with any of the comments - I was just looking at options, but to a price. Given the OP original budget and FL requirement it would still be an option in my opinion. With a flattener reducer it would also give quite a fast system for AP.

Personally I would go with the RC6 with a suitable flattener/reducer and bin the camera. This would remove the false colour and give a fast system at a good sampling rate. Good value too.

29 minutes ago, Adam J said:

I dont see that as being an imaging scope more wide feild visual. You are going to see significant blue bloat from a  110mm FPL-51 doublet at F6

There will undoubtedly be some CA at F6, but nothing that could not be removed relatively easily in processing or with an L3 filter. However, looking at the specifications again the Starfield is probably a better bet.

I do think there is a bit of an obsession with FPl-53 over FPL-51. A well made FPL-51 is likely to perform as well as 53

I have not used one, but I am guessing your EQ2 with a RA motor drive would be usable as a star tracker. You can use this to mount you camera as a starting point. Next stop I would suggest would be fleabay. There are expensive ED lenses which are ideal for AP, but to start with a standard widefield lens or two would get you started without having to empty your bank account. I just got a 100mm F2.8 prime lens for £30. This plus an intervalometer for the camera will get you started as a very simple set up. Yes, it will not give perfect images but you will be surprised what you can achieve. It will also allow you to try stacking and image processing before entering the financial black hole of AP. Trust me, it is addictive and expensive😁

The other thing to consider is the mount. For the longer FL you will need good tracking.

What about the SM 110mm F6 doublet? Slightly more money but probably better suited to AP and a good price.

I think they are generally quite well collimated out of the box. I think many have been made worse by 'tinkering'. My method for collimation is to remove everything xcept the focuser and get the secondary perfectly aligned. I use a TSKOLLI or Reego, but you can use a simple Cheshire for that part. Once the secondary is right I use the DSI method for the primary using a star test.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.deepskyinstruments.com/truerc/docs/DSI_Collimation_Procedure_Ver_1.0.pdf&ved=2ahUKEwi62bCmhJX5AhVMPcAKHcvBBws4ChAWegQIKBAB&usg=AOvVaw1TQ8YAhohC9_gr_IRXBo3x

This works for mine but my focuser and primary mirror appear well aligned as I get no tilt issues. If this is not the case it is more tricky - but the DSI method should still work. My main advice would be adjust it SLOWLY and try to remember what you have done to put it back again.

There is not a lot to say about the scope itself. I do have a home-made secondary dew heater, but I have never had a problem with the primary and dew. Cool down is pretty rapid too as it is an open tube. I have only used it with a ASI1600 which gave a good flat field. With a larger sensor you might need a flattener. I still need to try it with my IMX571 camera to determine if it is OK with and APS-C size sensor. I did change the focuser to a Baader ST. The original was OK in terms of tilt, but it did slip slightly with the autofocuser. I hope this helps. Here are a couple of images with the scope. Just remember I am far from an imaging expert!

Still a couple of weeks to go☹️

As an RC8 owner, I must say I am a fan. In terms of value for money I think they are excellent. As I am sure you have read, collimation can be a bit tricky initially - but once set it does not need much adjustment. I typically bin 2, but in all honesty, with my seeing bin 3 is probably more realistic. Also, although F8 it never 'feels' slow except when compared to my F4 scope.

I have used Cheap Astrophotography as have many others on the forums. Juan provides a good service and sells ready modified cameras.

23 hours ago, Anthonyexmouth said:

Windows to an nvme drive I have spare instead of the emmc that it comes installed on?

FWIW I use a Mele Quieter 2 and I added extra nvme for data storage but left the operating system and programs on the existing emmc. Technically it may be better to put everything on a new drive, but I have had no issues running 2 x NINA with PHD2 on my dual rig. If it ain't broke.....

How about a 115mm triplet such as a TS photoline? There are a number of 'clones' too. Probably the limit for an HEQ5 but could be used at native FL or with a reducer.

1 hour ago, SthBohemia said:

!! 82 quid for a handle that should be priced around 5 quid!!

It's astro gear. What do you expect?😆

I have 2 Baader ST's, one on my 6" f4 Newtonian and one on my RC8. I found them to be excellent for imaging.

With regards to the scope collimation, the f4 is a right PITA to collimate. I share your pain. However it is much better with a good focuser - the original TS one was pretty awful. Maybe avoid the laser if you are struggling with it?

I used to use a 12v powered hub on my mount, chopping off the 240v plug and replacing it for a 12v. This was connected to an active cable.

https://www.amazon.co.uk/RSHTECH-Powered-Extension-Charging-Individual-Red/dp/B07RS31T3Y/ref=sr_1_9?crid=1BHL2DWLICKVV&keywords=12v+usb+hub&qid=1658258974&sprefix=12v+use+hub%2Caps%2C147&sr=8-9

Most of the time it was OK but it did get temperamental with my ASI1600. Eventually I changed to a mini PC on the mount (Mele Quieter 2) which I should have done from the start. Works very well and no connection issues.