symmetal

Bresser, Germany emailed. Thanks altocumulus. Afterward, I took out the blue glass filter to see if it could be cleaned but only the spot in the middle came off. The deposits around the filter edge are actually on both sides of the filter and about similar sizes. With the blue glass removed and looking inside there is what looks like a white powdery deposit all over the black housing holding the prism. It doesn't seem to come off when scraped with a cotton bud. It may be that the black coating on the housing inside is just 'over-spray' and it's the bare aluminium or whatever it's made of showing through. Also, looking into the prism you can see the rear side of the filter after the prism. It looks orange but I think that's the prism causing this. This filter however looks to have a film covering most of its surface which doesn't look good. I tried to photograph it but it didn't come out all that clearly. 'White powdery coating' inside BF Film on rear of filter looking through the prism. Does anybody think it's worth asking Lunt about this? Alan

To help bilbo out with his blocking filter survey I checked it and found this. It's only about 2 years old too. Is it best to contact Bresser Europe or Lunt USA for the free replacement filter? Alan

Hi Steve, my B1200 is green. S/N 0001005 Alan

James is right though it's about 90 deg c/w from normal view. Download the free Virtual Moon Atlas and you can easily identify all the features. Alan

CCDI ignores clipped stars which excludes most of the stars in R3tro's image as the image has been stretched. Only dim indistinct stars are left and CCDI only found 807 of them with the bulk of these being towards the bottom of the image hence the implication (by omission) that the top 2/3 of the image is good. Those near the bottom do show some distortion which is coma like but is not distinct enough to say for sure. CCDI reports it as tilt as that's its goto option when one side is worse than the other. A flat field with one side showing coma will be reported as having tilt. For CCDI analysis short exposures of 10 to 20s are best to avoid many clipped stars and image trailing from alignment/periodic error. Also no processing, and no need for calibration. Alan

Hi ippiu, I see you've decided to return the RC51 and the CEM25EC mount (having read the lengthy discussion on CN). As the final CN post says it's easy to get too involved on tests and not actually check what the final images are like after having stacked and processed many exposures. You may have found the slight edge coma shown in your test exposures would have been masked by the final stacked/processed image result and been hardly noticeable. Likewise with your mount. To get 'technically perfect' images you would have to spend a lot more money on the equipment, and so have to accept that there will be some flaws with your current setup, or any future setup that costs a similar amount. I agree that the RC51 shouldn't show coma and WO should really have this fixed before they released them, as it just seems to be a setup alignment problem, but yours was one of the better RC51s. Look at Davey_T's or helgeras' images to see what a poor RC51 looks like. Hope you manage to get something in the future that you like. Alan

As Dave said a single image is all you need. As the coma, if present, is usually more evident on the edges of the image, a larger sensor (as on a DSLR) will show problems which may not be apparent on a small sensor. If there is coma you can see it yourself visually when examining the image (especially in the corners) where the stars have fan shaped smears from the star centre. If you can't see any you're lucky and have a good lens. A fits file is the normal file format from astro cameras and the fits file header includes useful information about the image but isn't necessary. From a DSLR just convert its output file to a tif or png file, which CCD Inspector can read. I'm not sure if it can read DSLR raw files. The CCD Inspector just gives a more accurate display of the star shapes/sizes though will interpret coma as a curvature/tilt problem though that is not always the correct interpretation. The coloured CCDI plot is very useful as a quick check that the image is good or has problems. Alan

Also with less jpeg compression if possible as all the stars are hard edge clipped making their true shape difficult. Alan

The specifications of the relay board on the Amazon site does state ------------------------------ Features: 4-channel, DC 12V 30A relay module. Output capacity: within DC 30V 30A or AC 250V 30A. Using optocoupler isolation, strong anti-jamming capability and stable performance. The module can be set high or low trigger. To ensure stability, uses industrial grade PCB board and 9.5mm barrier terminals. All interfaces can be connected directly via terminal wiring leads, very convenient. Module Interface Description: 1. DC +: DC power supply positive; 2. DC -: DC power supply module negative; 3. IN: Signal input terminal(support High/Low Level switch freely); 4. Normally open (NO): Relay normally open; 5. Common terminal (COM): Relay common; 6. Normally closed terminal (NC): relay normally closed terminal; Specifications: Type: 4-Channel Relay Voltage: DC 12V Output Capacity: within DC 30V 30A or AC 250V 30A Quiescent Current: 5mA Trigger Current: 5mA Module Size: 128 * 68 * 20mm Module Weight: 177g ------------------------------------ To test just connect 12V to the relay board DC+ and DC - terminals and just connect one of the relay IN- terminals to the DC- terminal (which is the ground). If you hear a relay click when you do and click again when you remove the connection to IN- then it's working as we assumed and no changes need to be made. Alan

Hi Hugh, Good point. I was assuming the relay board acted similar to the ELK-924 relay board but that may not be the case. If the relay board input + and - do just go to an opto isolator then what you describe would need to be incorporated into the design. Hopefully some application notes or a circuit diagram came with the board and Peter can let us know what's what. The Grounds of the Velleman and relay board are connected so that's OK. Alan

5 Panel Mosaic using FLT-98, 2x Powermate and ASI178MM with Baader UV/IR Cut filter. 10mS exposures, Gain 60, Offset 100, 30s videos at 30fps. Stacked in Autostakkert, processed with Imppg and stitched with final adjustments in Photoshop. Click for full res. Alan

Teleskop Service sell thin stainless steel rings for fine tuning T2 spacing. They are available in 0.3, 0.5, 1.0 and 1.5mm thickness. They are not cheap but what price do you put on peace of mind. Alan

Are you using the spacers to get the camera rotation angle correct when everything is tightened up. Does your setup not have a built-in rotator somewhere in the imaging train for this purpose. Something like this T2 camera rotator might help or have I misread your post. Alan

Hi ippiu, I examined your 10 120s images and 10 180s images and they have all very similar star shapes, (if not exact). Here's the CCD Inspector curvature and 3D plot results of the average of the 10 120s images. The 180s images were the same. The pixel scale was assumed as they were png files so the arc-second values are not accurate though relative to each other it gives an idea. Also it is treating the coma as defocused stars so the actual curvature and tilt values don't really mean much. There is slight coma down the right hand side with the bottom right being the worst as before. When stacked and processed including debayering, it will give you a better idea of what the overall image is like and whether it is too noticeable. Many people would be happy with it, but only you can decide whether you are. It's not perfect, and you usually have to pay a lot more to achieve anything near that. Have you seen any images from the alternative scope you're looking at to see if it might give better results. Alan

Thinking further, the scope I used (FLT-98) is optimised to bring wavelengths passed by the L filter (300nm bandpass) to the same focal point. The IR pass filter from 685 to beyond 850nm, (runs off end of spectrum plot). The APO visible optimising could be creating havoc at different IR wavelengths with the focal point being all over the place. This would lead to softer IR pass images. If this is the case why is the IR pass regarded as the 'secret tool' of planetary/moon imaging. Maybe it performs better on an SCT or newt that it does on an APO frac. I think in this case a red filter would be better for me (and iwols) than an IR pass filter. Any thoughts? Here's a crop of two images of the same area taken a few minutes apart, both 10mS exposure and 30s videos, stacked in Autostakkert but no sharpening or other enhancements applied. The L is sharper. Alan

ippiu, The ASI1600 which I used when posting my test images is also a 4/3 sensor and they were significantly worse than yours. Using a full frame sensor the coma effects should get increasingly worse towards to corners though I haven't actually tried it so can't give you an accurate answer. Do you have a DSLR to compare it with. An APS-C is significantly larger then 4/3 so should show the worsening coma effect and give you an idea how the full frame might look. I'll examine your other images a bit later and report back. I think the WO claim is that it's the sharpest 250mm lens for full frame but as there aren't any others to compare it with, it can also claim to be the least sharp lens too. At the moment it seems to be a lottery as to what quality lens you get and if you get yours replaced you could easily end up with a worse one. Alan

I image the moon using an UV/IR cut (L) filter as well as an IR Pass filter to get seeing improvements as Olly says on the longer wavelengths. However the IR pass image is always softer than the L image using the same 10mS exposure and stacking 30s videos. I just use higher gain on the IR pass. I focus on a nearby star with a Bahtinov mask and have to change the focus between the two filters as you'd expect. Perhaps bahtinov mask focusing with an IR pass filter doesn't give the correct result but I can;t see why. Using the scope with a 2x powermate and working at f12 I wouldn't have thought the moon distance compared to infinity would have a more noticeable effect at IR wavelengths compared to visible. Alan

Hi helgeras, Yes, I'm afraid there is significant coma on the left third of your image as the CCD inspector image you've posted also indicates. CCD Inspector reports poor star shapes as indications of curvature and/or tilt though this is not always the reason for poor star shapes, coma being one of them. As I've found, the coma can't be improved by different focus so curvature/tilt is not the problem. I would say your RedCat needs to be returned. . Alan

Hi ippiu, I'd say you're RedCat is a good one. There is a hint of coma on the extreme bottom right but nothing that would cause alarm. The CCD Inspector analysis below indicates a slight sensor tilt from left to right which could be the reason for making the stars bottom right and top right very slightly misshapen as they end up being slightly out of focus. I assume this is using a DSLR? Overall I think you've got a winner. Better than I and Davey-T have. Don't worry about the first analysis looking worse than the second. Visually there's little between them.To get a proper analysis you need to take the average of several images. Alan

Hi Hugh, Thanks for the schematic. That explains why the clamp terminal is called that. None of the digital outputs are driving the relay coils or any inductive loads directly so the clamp connection isn't necessary, but no harm in connecting it to the relay board 12V. The pull up resistors to 5V on the digital inputs will put Peter's mind at rest too concerning the hall effect switch. Alan

Glad we got that sorted out Peter, and thanks Gina for the endorsement. Alan

Peter, No, you've misread my last post. There is no problem in powering the hall switch from 12V just as you've drawn it. Leave that as it is. Remove the pull up resistor on its output from the diagram. It's not needed when the hall switch output is connected to the VM110 digital input and it's causing confusion. As I mentioned above the hall switch output is not related to, or dependent on, the voltage used to power the hall switch. The voltage on the output is only dependent on the voltage supplied by a pull up resistor. When the switch output wire is connected to a VM110 digital input it is connected to a pull up resistor already mounted on the VM110 board digital input. The other end of this resistor will be connected to 5V. Any voltage you then measure on the switch output will only be 0V or 5V. The switch power pin sees 12V. The switch output pin sees 5V. Everybody's happy. By the way, you can't use a buck converter to convert logic signal voltages from one value to another. If you wanted to convert a signal voltage to a lower voltage you'd just use 2 resistors as a potential divider. Alan

Good detail and very clean images. Personally I'd use a little less sharpening but each to their own. I've just taken some L and IR Moon videos too but haven't processed them yet. Alan

Peter, There's no problem with the hall switch being powered with 12V as the switch output is open collector. This is a diagram of the hall effect switch showing the 3 terminals When the switch is off the output transistor is also turned off and its collector (pin 3) is effectively an open circuit. When the switch is on the transistor turns on (the collector to emitter junction becomes low resistance) and the output is effectively shorted to ground (pin 2). This is just how the reed switch operates when it is used instead of the hall effect switch. The digital inputs of the VM110 however want to see a change in voltage (0 or 5V), and not whether the input is shorted to ground or open circuit. The simplest way to achieve this is to connect a pull up resistor between the digital input pin and 5V. When the switch is off the digital input is pulled up to 5V by the resistor. When the switch is on the digital input is shorted to ground (0V) by the switch output transistor. The resistor can be a high value, 10k or more to avoid too much current drain on the 5V supply when the digital input is shorted to ground. If the switch was being used with a 3.3V logic board instead, the pull up resistor would just be connected to 3.3V. The pull up voltage is isolated from the hall switch power pin (pin 1) so it doesn't matter that the hall switch is powered from 12V. Hope this makes it a bit clearer. As I mentioned before there will almost certainly be a pull up resistor already on the VM110 digital inputs, so you won't need to supply an external one as well. Alan

Peter, Just noticed re the pull up on the hall effect switch. Connecting the resistor between the hall effect power and its output would pull the output to 12V when the switch is 'off'. This would mean the VM110 digital i/p gets pulled up to 12V too which could cause problems as the board is 5V powered. If you do want an external pull up resistor it has to go between the switch output and +5V. Omitting the external pull up is the best option as the board is almost bound to have one on the digital inputs. I didn't reply before, but you mentioned if the 3 diodes were necessary. The diode between Dig Out2 and Dig In4 on the VM110 is there to protect Dig In4 from rising above 5V if Dig Out2 is pulled higher than 5V by the relay board. Whether the relay board IN- inputs rise to 12V or 5V when the relay is off I don't know but it doesn't matter as the diode protects Dig In2 if it's 12V. The diode going to relay board NO4 is actually reverse connected across the motor terminals if you follow the wiring. This is there to protect any circuitry from the back emf voltage spikes generated by the motor when it turns off. Not always necessary but it's good practice to have one. The diode going to relay board DC+ is just circuit protection from accidentally connecting the lead acid battery the wrong way round. None of the diodes are passing much current so standard 1N4001 diodes or similar would do. Alan