Should I buy this?!

[JayTee]

Hi James,

Listen to Steve333. Then go to this website, CCD suitability, put in your scope and camera details, and judge for yourself. You will see that the guy on CN was mostly talking out of his butt. https://astronomy.tools/calculators/ccd_suitability

Cheers,
JT

[Baskevo]

Hi James,

Listen to Steve333. Then go to this website, CCD suitability, put in your scope and camera details, and judge for yourself. You will see that the guy on CN was mostly talking out of his butt. https://astronomy.tools/calculators/ccd_suitability

Cheers,
JT

That's what I used, as recommended by you when I purchased my ZWO asi1600mm Pro. He also recommended that tool to me and think the ASI1600mm still isn't a good match at 480mm. Here is what he says said about the CCD suitability tool:

I know you think your seeing is only okay but how did you measure it?

What the tool does not explain is that the imaging environment a dynamic. This is partially compensated for by the range of pixel size but that size is a single snapshot in time. If you have spent any time at all observing visually you know seeing and transparency are fleeting, variable and dynamic. Apply that knowledge to a syst that is collecting data over time.

So knowing how seeing conditions work and that it is constantly changing moment to moment how can we compensate or adjust to get the best imaging data? To ensure that you get the sharpest images possible you must be all the way to the left of the green zone to allow these moments of bad seeing to have minimal impact on your data collection and the moments of good seeing to not be lost to under sampling.

Think of the optum relationship between photosite size for the seeing conditions on a graph with this imaginary perfect pixel size as the vertical value and time as the horizontal value for the duration of your exposure. As you can see what we want to try to do is to put as much data as possible right on that line. But unfortunately the line is always changing up and down and our pixel size in the real world is fixed.

So to ensure the sensor size is always going to be at a minimum as close as possible but never dipping below the ideal we need to select our hardware to always be on the other side of that perfect line in order to accommodate the constantly moving ideal pixel size target. In other words we want to maximize the area under the perfect pixel size curve and to do this we must select a sensor size that falls on the side of oversampling the data.

So going through the suitability calculator, I am good with OK seeing and Poor seeing, but I am over-sampling at very poor seeing and under sampling at good seeing and excellent seeing...

I do not know how good my average seeing is...I just ran PixInsight's FWHMEccentricity script on like 10 images all from different nights (6 images after stacking, and 6 raw subs), and found my median FWHM for each image to be between like 2.4 px and 3.5 px, somewhere around there. Most of them hovered around 3 px. (I don't know if this is how you are supposed to measure FWHM, I was just trying it out). So that would mean I usually have OK seeing, right?

[JayTee]

James,

What the responder on CN is proposing

So to ensure the sensor size is always going to be at a minimum as close as possible but never dipping below the ideal we need to select our hardware to always be on the other side of that perfect line in order to accommodate the constantly moving ideal pixel size target. To ensure that you get the sharpest images possible you must be all the way to the left of the green zone to allow these moments of bad seeing to have minimal impact on your data collection and the moments of good seeing to not be lost to under-sampling.

is unrealistic in the "real" world of limited resources (ie money). Obviously he did not take into account what your setup is ideally suited for -- wide-field imaging. If you look at the negative side of under-sampling (and it's not all that negative), which occurs at only the very best of seeing conditions for your setup, it simply states that

Under-sampling reduces the influence of guiding errors and improves signal to noise at the expense of finest detail.

With an 80mm f/6 setup, you are not going for the finest detail because of your imaging scale. You are going for large objects (think M45 & M31). So with this in mind and given the "real" world constraints of what you can afford, you make the best of what resources you have. So go forward and start imaging.

And stop paying too much attention to the many counter-opinions over at CN.

Cheers,
JT

[Baskevo]

James,

What the responder on CN is proposing

So to ensure the sensor size is always going to be at a minimum as close as possible but never dipping below the ideal we need to select our hardware to always be on the other side of that perfect line in order to accommodate the constantly moving ideal pixel size target. To ensure that you get the sharpest images possible you must be all the way to the left of the green zone to allow these moments of bad seeing to have minimal impact on your data collection and the moments of good seeing to not be lost to under-sampling.

is unrealistic in the "real" world of limited resources (ie money). Obviously he did not take into account what your setup is ideally suited for -- wide-field imaging. If you look at the negative side of under-sampling (and it's not all that negative), which occurs at only the very best of seeing conditions for your setup, it simply states that

Under-sampling reduces the influence of guiding errors and improves signal to noise at the expense of finest detail.

With an 80mm f/6 setup, you are not going for the finest detail because of your imaging scale. You are going for large objects (think M45 & M31). So with this in mind and given the "real" world constraints of what you can afford, you make the best of what resources you have. So go forward and start imaging.

And stop paying too much attention to the many counter-opinions over at CN.

Cheers,
JT

Haha thanks for easing my mind, JT... I figured he was talking about incremental improvements, but he was making it sound like it is life or death--like I had to be in that range to have a decent image at all. It didn't sound right because I see the ASI1600mm/ED80 combo everywhere.

I also image 100% from my backyard, and while I do want to make it to a dark site, the most I'd ever be able to go is once a month or so, and that's if I'm lucky. And with starting law school in the fall, who knows if I'll ever be able to make it to a dark site, let alone image at all. So I'm pretty sure I'll be stuck with at least a bortle 7 for quite some time now (the bortle scale for the surrounding areas is playing a role in deciding which school I go to lol)

To be fair to myself, I did not ask for his opinion. Lol he reached out to me through my classified ad as I'm looking for a field flattener for my new SV...

Anyway, good news! I finally found an AT2FF field flattener for my ES I'll probably end up selling it, if the SV is an improvement, but I've been looking for one for so long that I had to buy it and try it out lol

[JayTee]

James - Don't sell the AT2FF just yet. It is a very handy accessory to have, you may actually need it for the SV.

JT

[Baskevo]

James - Don't sell the AT2FF just yet. It is a very handy accessory to have, you may actually need it for the SV.

JT

Good to know! Thanks JT

[Baskevo]

Hey guys so I received my scope today, and everything looks fine, but I am hoping someone like [mention]Lady Fraktor[/mention] can confirm that it is the correct scope. I don't see anywhere on the scope or in the manual that it is actually an FPL-53. Here are some pictures:

The rings also seem that they might be too small for the scope, as they aren't totally straight

[Lady Fraktor]

When I was discussing the refractor with you the other day, Stellarvue build sheet lists these as being FPL-53
Enjoy the new telescope!

[Baskevo]

Okay good thanks Lady Fraktor! I hope I will enjoy it.

I am really over the ES and issues with balance. As cool as it looks, I feel that the side-by-side setup makes it a lot harder to get good balance. and because I have have the rings so close together to place the guide scope on the rig, I'm pretty sure I'm getting flexure. Tonight was the first night trying out the new mount (the third one, after sending back the first two because of issues), and my guiding is horrible--worse than with the AVX. I think it would be statistically impossible for me to get another bad mount for the 3rd time, so that leaves either sky conditions that are too bad to get good guiding, or my guide scope as the issue. I don't think it's the sky conditions because with the coronavirus, I expected this to be a really great time because of less smog from driving, and I have had good guiding with the EQ6-R Pro before.

As much as I love it, this hobby can be so frustrating.

[Lady Fraktor]

Ever thought of just doing visual? Much more relaxing

Usually the rings fit quite snug on these, does it look like perhaps the last owner changed the felt to some that is slightly thicker?

[Baskevo]

Never!! ;P AP is frustrating, but worth every hair pulled!

Well they are snug... it just seems that the rings are a little bigger than a perfect fit, so the top of the rings where you would put a find scope is pointing a tiny bit off to the side. Does that make sense? So yes it could be possible that he changed the felt, but I feel like he would have mentioned it if he had.

Just ordered a ZWO 60mm guide scope--hopefully that will give me some better guiding!

Update though--I'm getting some pretty decent guiding right now, at .70 and .45 RMS errors. I don't know if it's because it got darker, or if because I'm pointing higher in the sky. At least I'm pretty sure its not the mount now!

[Baskevo]

When I was discussing the refractor with you the other day, Stellarvue build sheet lists these as being FPL-53
Enjoy the new telescope!

Hey Lady Fraktor, do you know what thread the 25SV focuser uses? I am trying to find an adapter to thread my blue fireball 360 degree rotator directly into the focuser...

this is the rotator, which has m54x0.75 threads: https://agenaastro.com/blue-fireball-36 ... -r-03.html

What I did with my ES was thread the field flattener directly into the rotator, which is what I would like to do with my Stellarvue, but I can't find any info on how to do that.

[Lady Fraktor]

I will ask my friend if he has the specific thread, would it be the same as the TeleVue FF I linked the other day for you? The threads were listed on that.
You can also contact Stellarvue themselves, they are always helpful with this kind of thing.

Stellarvue
11802 Kemper Road
Auburn, CA 95603 USA
(530) 823-7796