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Raffaello Braga
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[2018 August 07] Solar activity continues to be very low, but a couple of pores appeared at high latitude few days ago making - may be - the first signs of cycle 25th.

Today the Sun is blank in WL, in Calcium light it shows two large irregular plages that have counterparts in H Alpha also. SDO imagery doesn't show any active region behind the east limb.
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[2018 July 19] Another spotless day, the photosphere is blank apart from some facular regions visible close to the east and west limbs. The chromosphere in the Calcium H line shows a number of bright regions and the usual supergranulation network but no further details.
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[2018 July 18] Is solar minimum really approaching as explained by Spaceweather.com ? May be as the Sun is still quiet. However even in WL some activity can suddenly appear at any moment as occurred this morning around 6:20 UT, when a small, elongated and very dark spot appeared in SW quadrant in a small facular area. It lasted 10 minutes only leaving a grey ghost behind but it was a fine sight in my 80 mm apochromat. In fact the study of these short lived featured would be a very interesting field of study for the skilled amateur.
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[2018 July 16] Sun activity is very low with no sunspots on the visible surface although a large plage can be seen in Calcium light. In the past two days small pores suddenly appeared close to the centre of the disc but today I couldn't find any traces of them.

The sunny day allowed me to do an interesting comparison between my 80 mm f/11.2 TMB-designed achromat (the so-called Planet Hunter) and my SW 80ED f/7.5 in imaging the disc in Calcium H light. It is well known that long focus achromats can be very well corrected not only in green light but also in violet light due to their inherent low spherochromatism that make them excellent instruments for narrowband imaging of the Sun. Faster achromats show more and more spherochromatism and in fact my 150 mm f/5, an extreme case with a CA index of 0.85, can't form a sharp image when used in violet light and needs to be stopped down to at least 75 mm (f/10).

The attached images taken with same seeing, acquisition and elaboration show that both the above mentioned instruments performed very similarly in the near UV. This means that the designer of the Skywatcher apo made a particularly good job in correcting the objective (for spherical aberration) at short wavelengths. In the red region it is less corrected but is still capable of delivering very fine images in H-Alpha light.

The darker areas on both discs is due to some dirty spot on the CCD... 😫
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16/07/18
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[2018 July 02] Today is the fourth consecutive day without sunspots after the burst of activity of the past weeks when Wolf number rised above 60. Only in H-alpha there are some small prominences and few very minor filaments while in Calcium light the disc is mostly featurless. Based on SDO images no news are expected at the moment although small short-lived pores appears regualrly in WL using high magnifications.
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02/07/18
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[2018 June 25 to 29] Sun is again returning to low actvity while AR12715 disappears behind the limb leaving no spots to be seen. Even in H Alpha activity is very modest with few minor prominences but with a quiescent tree-shaped one that seems to persist in these days. The Calcium-H disc is almost free of plages.
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28/06/18
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Almost solved the problems I had with my Lunt LS50THa solar scope in making full discs of the Sun. I always found difficult to obtain a disc of uniform brightness but I discovered that rotating the diagonal with the eyepiece holder at 9 o'clock position (looking at the scope from behind) produces an acceptable result, much better than those I obtained up to now.

I think that there could be some kind of mismatch between the BF and some internal component of the tube, rotating the diagonal probably help to compensate the problem. Turning the tuning knob has also some effect as it makes the disc brighter or darker.
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[2018 June 16] A drawing of planet Jupiter made with my restored Planet Hunter 80, by TMB/Astro Professional. I am really happy of this instrument, it provides perfect textbook diffraction images and an excellent correction of the chromatic aberration, much better than most 80 mm achromats. Jupiter was very sharp and steady, in spite of the low altitude above Milan sky. I barely detected a couple of festoons descending from the NEB into the EZ but the view was uncertain (these details are at very limit of an 80 mm scope) and I didn't report them in the drawing. Two dark condensation in the NEB were much clearer as well as some subtle bands as STB and NNTB.
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22/06/18
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[2018 June 21&22] Solar activity is still moderately high. Active Region 12714 is gone behind the limb, 12713 is approaching the west but remains in evidence and seems still growing. On June 21st AR12715 produced a C-class flare and continues to be an interesting feature for telescopic observers. The large active area emerged from the E limb remains spotless but is prominent both in CaH and H-alpha light as can be seen from the attached images.
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22/06/18
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[2018 June 19&20] An abrupt increase in solar activity led to the appearance of four active regions with an overall Wolf number of 61 for the first time in months. AR12713 is still alive and new tiny spots appeared in the last three days. AR12715 is of C-class and shows a leader spot with a defined penumbra. Is a fine group, yet a modest one, very interesting to see at high magnifications. The larger active region that is rotating into view does show only a bright plage but apparently no sunspots.
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20/06/18
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