13 replies to this topic

[pyrasanth]

I've noticed over many months a very substantial deterioration in the quality of my local sky. There is not really a solution other than move house which for most people is not an option.

 

I've found as part of this down hill slide that the C14 is not used as much- it simply does not have the conditions to shine- I feel it is very much seeing limited.

 

I've decided to give the C14 a rest and dismount it from the Paramount and replace the OTA with the RASA V2 11" and a CMOS ASI2600 colour camera (I have the mono version as well however this will fit into a plan to be indicated later).

 

I fitted the Pegasus Falcon V2 rotator to the Altair ETX-115 APO yesterday. Since I had to purchase custom adapters to fit this I was able to precisely get the back focus correct. On the full frame ASI6200 camera I now get very sharp stars right to the edge of the field. This little refractor, I believe, can resolve right to the limits of my local seeing conditions. I've compared the details captured with the C14 and all I seem to be getting is a bigger image with not much more detail.

 

My testing moving forward will be to image RGB with the RASA & use the Falcon rotator on the ETX-115 to rotate to the RASA image. Nothing is lost in this testing as obviously I still have the C14 however I will be looking at its future a bit more closely.

 

The test image is for 6 hours on the ETX-115 of the M106 region around a 70% of the available field - the stars in the full frame are sharp to the very edges with or without blurxterminator which just pulls in the objects tighter.

 

The image is 6 hours of HA captured under a full moon with the Max-FR Astronomik 6nm HA filter and Altair ETX-115 APO on the ASI6200 1x1 bin.

 

Let me know what you think- am I doing the right thing?- all observations considered.

 

A larger image for you pixel peepers is here https://www.astrobin.com/595qqh/

 

Edited by pyrasanth, 16 March 2025 - 05:53 AM.

[ayadai]

Maybe send the C14 to StarFront?

[Mert]

Good detail in there Mark.
Even the anomalous arm shows up very clearly!

Edited by Mert, 16 March 2025 - 06:53 AM.

[BucketDave]

I'm coming to the same conclusion with my ACF (at F10) but due to light pollution. I can image for a night in the garden (B6/7) and get a so-so image. Or i can pop down to the Mendips (an hour away) and get a far better picture in B4 skies. It's less convenient but for the sake of £40 for petrol, campsite fees and a meal in the pub, what's not to like?

Another factor is that the ACF optics aren't as sharp as they could be. So it's making me wonder if a 4" refractor is the way to go. Speed seems to be a big player unless you want to do planetry imaging.

[pyrasanth]

Maybe send the C14 to StarFront?

The price for a large pier is somewhat eye watering- not an option for me as I'm not rich!

[pyrasanth]

I concur with Bucketdave- I simply don't get enough clear nights to use the C14- it would take me typically 3 seasons to get an image I'm happy with. The RASA will pull all the required RGB in one session of 8 hours. We have to now begin to think smart- the Bortle 4 sky you see is a very good real option. I would have to think portable!

Edited by pyrasanth, 16 March 2025 - 06:56 AM.

[pyrasanth]

Good detail in there Mark.
Even the anomalous arm shows up very clearly!

Thanks Mert- the 4.5 inch refractor is amazing especially now with the back focus dialled- really nice details being picked up- its a good optic. One thing I sorted was a dew band that was too long wrapped around the OTA- that gave too much heat and it caused, I think, little spikes on the stars as the optics perhaps were being distorted due to too much heat. Since I changed to a dew band of the right size the spikes on the stars are very much reduced.

[Scott Badger]

I have poor and highly variable seeing, but one strategy to make the best of what I’ve got is to shoot lums (or Ha for emission nebulae) only when seeing is best, and R, G, B otherwise. Less color resolution isn’t an issue if you hav a higher resolution luminance.

I’m curious though what you think is driving the deterioration of your seeing. I’ve heard concerns that climate change is increasing cloud cover, though I’ve also heard it can cut both ways in that regard, but I haven’t heard reports of a change in seeing conditions….is the difference between your day and night temps increasing?

Cheers,
Scott

Edited by Scott Badger, 16 March 2025 - 07:34 AM.

[alien_atx]

The price for a large pier is somewhat eye watering- not an option for me as I'm not rich!

Your C14 should comfortably fit into a Starfront standard pier with a 58" swing diameter at $299.....

 

You can find another astro buddy to share this costs.

[Spaceman 56]

Sad to hear of your deteriorating skies Pryasanth.

 

My Bortle 1 skies are also deteriorating, due to that dam Elong Musk, and his cursed Sate-Lights coming over every 5 minutes or so.

 

I have reduced my sub exposures to 120 seconds because of this.  

[pyrasanth]

Sad to hear of your deteriorating skies Pryasanth.

 

My Bortle 1 skies are also deteriorating, due to that dam Elong Musk, and his cursed Sate-Lights coming over every 5 minutes or so.

 

I have reduced my sub exposures to 120 seconds because of this.  

I feel your pain. I'm seeing a general loss in sky quality- the air does not seem as clear as it was a few years back.

 

We need better tools to deal with the sat trails- rejection unless set up carefully can leave traces in the masters. I try & rely on total removal of the affected subs but this needs a lot of pre processing blinking. I do lose a lot of data however until I can rely on total removal of sat trails I don't see any other alternative.

[ayadai]

I feel your pain. I'm seeing a general loss in sky quality- the air does not seem as clear as it was a few years back.

 

We need better tools to deal with the sat trails- rejection unless set up carefully can leave traces in the masters. I try & rely on total removal of the affected subs but this needs a lot of pre processing blinking. I do lose a lot of data however until I can rely on total removal of sat trails I don't see any other alternative.

The burgeoning satellite population is the biggest threat, IMHO. I chronicled some recent experiences in this thread. I also remove the most egregiously damaged subs; residual artifacts subsequent to rejection stacking have become the norm as of late.

[lambermo]

the stars in the larger image at 100% look perfect to me

and i'm amazed at how much data you got from the galaxy with just Ha

 

For the comparison of the ETX-115 and the C14, both with the asi6200 I'd like to use my own tool: https://lambermont.d...d2=115.0&f2=7.0

 

 

So the refractor has a 19x larger field of view, and a 2x larger 'speed' (extended object irradiance), a 2x larger etendue and pixel etendue and pixel signal, but a 4x smaller point object irradiance and an 8x smaller object signal compared to the C14

Edited by lambermo, 17 March 2025 - 08:43 AM.

[pyrasanth]

the stars in the larger image at 100% look perfect to me

and i'm amazed at how much data you got from the galaxy with just Ha

 

For the comparison of the ETX-115 and the C14, both with the asi6200 I'd like to use my own tool: https://lambermont.d...d2=115.0&f2=7.0

 

2025-03-17_14-31.png

 

So the refractor has a 19x larger field of view, and a 2x larger 'speed' (extended object irradiance), a 2x larger etendue and pixel etendue and pixel signal, but a 4x smaller point object irradiance and an 8x smaller object signal compared to the C14

Thank you for the comparison data. It would be useful to explain your findings in the context of real world results.

 

I have done a lot of work with the Altair ETX-115 with a focus (excuse the pun) of making sure that focus is very sharp & frequent refocusing happens. The mount is also under subscribed for the OTA so it has no trouble handling the OTA- it's on a CEM120. The choice of filters also helps- I'm using the Astronomik 6nm range optimised for F8 and lower. It all adds up to a pretty premium system- I really like the results.

 

I've just fitted the Falcon V2 rotator. This will allow me to align the RASA RGB to anything I decide to complement with the Altair refractor. I'm looking forward to the results.