Adam J

Oh if its just CCD inspector and its not related to what you are actually seeing then I would chin CCD inspector off, I have always considered it to be inconstant at best. If you are using NINA then try the Hocusfocus plugin instead. Adam

Sorry NO i don't mean for you to do it yourself at all! I mean that your retailer might be able to do it for you or SW. Never mess with those yourself. If you accidentally de-centre a lens element you will not get it reentered without specialist equipment. For that matter if you turn it the wrong way and tighten it when its already tight worse case you can crack a lens element. Adam

So you focus, it gets gradually worse with each image, you refocus and then its back to being good again? Very odd as I would normally expect focus drift due to temperature change to have a more global effect on focus but the above is indicating tilt.... So tilt is changing over time.... Can yo notice any physical lateral movement in the focuser tube? The images are not ruined BTW. You can create two stacks, one using all the date, the second using just the data with good stars, they you remove the stars from the stack with all the data and process the good stars in from the other stack...assuming your using starless processing anyway. Most do these days. Adam

What I would say to you is that as the problem is not present at room temperature the solution may be to just to slacken each of the centring screws a tiny bit.

Not clips, clips are for Newtonian, they are caused by the lens centring screws pushing on the edge of the lens elements. Its annoying really because the Esprit lens cell has design elements to reduce the chance of this cork buffers between the grub screw and the lens and so this is realistically most likely being caused by pure human error in over tightening the adjustment screws or forgetting to back them off once the lens retaining ring has been tightened. Very frustrating.

Great work with the star test this is exactly what I needed to see. So what I am seeing is two problems probably linked. 1) You have a turned edge indicated by the fuzzy outer difration ring here. But that is probably largely being caused by the second issue. 2) In my opinion you do have pinched optics which simply should not be occuring at +5c in any scope, you can make an argument that in mass produced scopes some amount of pinching has to be accepted at sub zero temperatures. But +5c is right in the heart of the temperature range that you are going to be doing most of your imaging in the UK during the autum and winter months and the problem is that on the nights when it is -5c its going to get much worse. The second thing that tells me its pinching is that it is not visible in the room temperature testing you sent in earlier. Here is the best image showing the pinching: I have pointed out the 6 x small dark notches in the outer diffration ring here. As noted above the Esprit doesnt have lens clips, it uses a continual ring gasket to space the lens elements and so the only explanation for such a perfectly symetrical pattern is pinching by the 6 evenly spaced lens centering grub screws used on the esprit. This is so caractoristic of the Esprit (so few manufacturers using 6 centering screws) that if you showed me that star test without knowing what scope it was I would guess its a Esprit and that its pinched. Its normally harder to see the effect on the other side of focus. But in this case I can just make out the 6 bumps in the outer defration ring (opposite side of focus opposite effect). It could use more exposure but the in focus image is starting to show the fluring that is associated with the pinching. On the bright side colimation is ok. So my bottom line opinion remains the same as it was following my assessment of the jelly fish nebula image you posted and that is that the lens is pinched. The pinching is visible in the star test and in focus star at temperatures of +5c and (potentially higher), the effect is not confined to the halo of bright stars, extends to background stars and this is sufficient to cause amounnts of aberation so as to detract from the image. So thats my assessment, but I dont want to tell you what to do, as thats your choice. The corner star shape issue is caused by incorrect back focus unrelated to the pinching. Hope that helps. Adam J

The manufacturers do it because up till now we have all been too trusting or not sufficiently informed, if the ability to check filter performance proliferates then they will be forced to reject more filters. Rejecting more filters will almost certainly cause prices to increase in any case. In this way binning filters for performance against F-ratio could actually keep prices lower for the majority while forcing those imaging at F2 to pay more for the privilege of imaging at a more challenging f-ratio. Adam

When you get a chance try a range of differnt focus positions from in focus to a size like your original images and ill take a look.

I have not really experianced turbulance like that from an airtificial star normally its too close to see anything, did you let the scope cool to ambient once you got it outside. I would also say that its still too big though better, but I am starting to see some potential notches in the outer ring. Adam

Its none of the screws on top don't touch those as they hold the linear bearing in place and if that falls out its a world of hurt. The adjustments for the friction pads are on the bottom sides, diagonally into the body of the focuser. You will find 4 of them two either side of the focus nobs, whatever you do don't loosen them too much or again the linear bearing will fall out. They are little grub screws that are basically pushing up against the tube via a Teflon pad and hence ultimately up against the linear bearing holding it in place. Its difficult to say as you are too far out of focus, the further out of focus the less sensitive the test as the errors blur together. But having said that I dont see anything obvious, noting that room temperature is a long way from any temperature you are likely to be imaging at. I would say you need to be at least half the size of this one. But you need to be at more like 5c than room temperature. However, a comparison between this and any current outdoor temperature will be informative. Adam

I think your assuming allot about how its deriving its data, I doubt that its actually referencing voltage ratio all the way back to derive a received power ratio, to do that it would need to understand the pixel value in terms of e/ADU. I would be shocked if the algorithm has that information avaliable, more likely its just looking at the pixel values and using the deviation of those values from the average referenced to the offset (signal). Hence 10 Log could well be more appropriate. Adam

Your back spacing is indeed wrong, that is the problem your seeing in the corners, what we are looking at are the hexagonal shaped stars and the dark wedges within the star halo that align with the points of the hexagon indicating that the optics may be pinched. Normally the other possible cause is lens spacers, but that just cant be the case in a Esprit 100 as individual spacers are not used. The lens elements are separated by a thin plastic gasket ring that is complete around the perimeter of the lens element and these are not visible without taking the lens apart. Reference: http://interferometrie.blogspot.com/2014/08/esprit-tuning-how-we-finetune-esprit80.html The early Esprit models could have a gap in these rings causing issues but this was addressed quite some time back by SW and you should not see this on a modern model. Back spacing will not effect the shape and halo of stars in the centre of the field. As a note its hexagonal as opposed to a Maltese cross or triangle because SW use 6 adjustment screws not 4 or 3. Some have 3 which would give a trefoil aberration, reference: https://www.cloudynights.com/topic/697015-what-is-a-pinched-optic/ https://www.cloudynights.com/topic/691489-poor-stars-with-esprit-80ed/ But I don't want it to just be my assessment, so it would be good to get another opinion from other members with the required optical knowledge. What I would do is get an artificial star and do a star test (De-focus either side of focus by 3-5 diffraction rings) if you see indentations in the outermost ring then that indicates pinched optics. It is 100% possible that ambient temperature is playing a big part but personally i tend to think that temperatures above freezing should never result in this issue as this is not primarily a summer hobby. So i would re-test on a milder night and see if you still see this and if you continue to see issues at temperatures above freezing then that is really not right in my book. My Esprit will not show that effect at any temperature I have used it at (touch wood) and I have imaged down to -5c at least. Adam

Its less a know problem with the Esprit than it is a problem almost universally, you will see examples of pinched optics from all makes and models of refactor unfortunately. I have even seen clear cases from Takahashi. SW sell lots of these scopes and so it will pop up from time to time. Its certainly not a design issue. Adam

13m is not sufficient for a 130mm triplet assuming its about F7 then about 25m is the minimum. Also you want to be viewing the star out of focus so you can see about 3-5 diffration rings to perform a proper star test. Adam

As above you should return this its within warrenty looks badly pinched. Adam

Its similar to the issue i had with the scope i returened a few years back yes, but I would actually say this is much worse, its certainly looks like badly pinched optics to me and I would be returning this scope if it was mine. Adam

I tend to remove LP1 in any case as its also the anti-aliasing filter and thats no good for astronomy. So dont assume that they did not remove it just because its a hamod.

My main concern would be flex in the wheel causing tilt due to lack of rigidity. How easy is it to produce your own ascom drivers, never investigated it. Adam

So 10dB = 1:10 20dB = 1:100 30dB = 1:1000 40dB = 1:10000 So not sure how you are getting 1:100?

There is a piezoelectric vibrating element attached to LP1 so it depends on if they removed both filters of just LP2 during the upgrade.

Yeah I can't agree that duel band are on par with mono narrow band filters either. I can certainly tell the difference.

Get a mono, no question in my mind about that. I am going to be controversial and say that I tend to enjoy OSC images less than equivalent Mono images even with the latest CMOS OSC offerings and duel band filters. Now that's not to say I don't enjoy osc images at all or find value in them, but if I made a list of my top 10 favourite images on astrobin all would be shot with a mono sensor. A OSC camera is a fantastic tool in many scenarios and makes sense on some scopes like a RASA. I would consider owning one as a second camera. But for me mono is still the king of DSO imaging by a none trivial margin. Adam

The FRA300 would be my choise the redcat 71 in my view is a little weird having a helical focuser on such a large scope. Adam

Depends how its measuring SNR. But a SNR of 1:10000 seems unlikey as thats almost what i would expect from a daylight image lol. Adam

My guess would be that the values the SGP is using are relative gain so 100 = 1x However, the camera has two read modes. LCG = Low Conversion Gain and HCG = High Conversion Gain For DSO imaging you want to be using HCG and I have no idea how you select that in SGP. It may be that it sets HCG automatically for gain values higher than 200 according to some documentation, but even that is complex as some imaging software will perform the mode switch automatically and some will not. Unity Gain is what you should use for RGB imaging and that is gain 282. That would correspond to a relative gain (assuming that is what SGP is using) of 2.82 of if SGP is using dB 4.52. However that could result in a relative gain of 5.65x if switching is automatic. So you need to find out what units SGP is using for gain and if its automatically switching from LCG to HCG. The end point for me with this is that the SGP implementation is a mess and so perhaps you can just set gain in the ASCOM driver instead of in SGP? In terms of such problems I would call this yet another reason to convert to NINA from SGP. As in NINA you just use the 100 - 4000 gain range and you can reference that the the sharpcap sensor analysis charts that have been published. It seems to me that as you have paid good money for SGP they should be bound to help you if you send them an email. Good Luck Adam